Our body has specialized nerve fibers, which detect potentially dangerous changes in temperature, chemical balance or pressure. These "danger detectors" are called "nociceptors" and send alarms to the brain: they cannot send pain to the brain because pain is a "brain product", an "output" in practice.
The pain is not actually produced by the wrist you have broken, or by the ankle you have sprained. Pain is the result produced by the brain that evaluates information, including danger data, cognitive data such as expectations, previous exposure, cultural and social norms and beliefs and other sensory data such as what you see, feel at wrist or ankle level and, this interaction of data, becomes what you perceive.
I see that it can be complicated to understand. This is a difficult concept to explain, but I try with examples. Try to think of a runner who finishes a race, despite a sprained ankle that he got during the race, and that begins to perceive the pain only at the end of the competition: maybe something similar happened to you too. Or you can think of a soldier in war, with a serious wound, but who feels no pain, because at that moment his brain needs him to escape and to save himself. Obviously the tissue is involved, it has obviously suffered potential damage, but it happens, in some moments, due to the context in which the damage occurs (the race and the war, in our case), that the brain considers it as secondary. Strange, isn't it? It doesn't just happen to sportsmen or soldiers. It happens to everyone.
The brain produces pain by creating the "best possible scenario", based on all incoming data and stored information, always in order to protect ourselves. Usually the brain does this well, sometimes not.
Nowadays we know that pain can be "activated" or "increased" by anything that gives the brain credible evidence that the body is in danger and needs protection. When we say this, we do not think on a large scale: we are not referring (only) to catastrophes, serious threats, predators, nuclear wars and the like. We think of wrong beliefs about our problem that leave us with an internal sense of fragility, such as when we face activities that we consider harmful to us, or we are in a vortex of negative thoughts that paralyzes us in the face of pain and that makes any small thing seem an insurmountable problem. Leaving aside for a moment the concept of protection, other factors such as lack of sleep, lack of physical activity, stress, anxiety ... can make our body more sensitive to pain.
This should not lead us to think that pain is a phenomenon that concerns exclusively the brain and not the body. In fact, nociceptors are distributed on almost all of our body tissues and their role is to send information to the brain about thermal, chemical and mechanical changes. For example, when the temperature increases or decreases, when someone touches us, presses, they send information to the brain which, eventually, puts in place defense strategies, such as the repair mechanisms that we have all experienced in life after, for example, a sudden ankle sprain.
It is normal that, after a traumatic event, in the first few days there may be inflammation, which makes the affected area more sensitive. Inflammation, on the other hand, by making the affected areas more sensitive, causes them to respond to stimulations that aren't really dangerous. For example, when we move the aforementioned sprained ankle a few hours or days after the triggering event, it hurts particularly with even minimal movements. This can obviously happen in any part of the body: in the back, neck, shoulder, etc.
However, it is also common that the situation returns to normal within a few weeks or at most a few months. In the absence of severe neurological, rheumatological or malignant conditions, what is not normal is that the same activities that were painful or difficult in the early stages persistently continue to be painful. This is referred to as persistent pain and requires a different approach than acute pain.
Treating a persistent pain as if it were acute pain is one of the most frequent errors in which a patient and a healthcare professional tend to incur. Instead of being helpful it can be counterproductive.
There are no magic pills for persistent pain, but you will be pleased to know that, being our plastic system, recovery in certain situations can be quick. Other times this requires a journey of patience, perseverance, courage and good preparation. This depends on the factors that underlie your problem and that we will understand better later.
If you understand little or nothing about everything I've written above, you have all my understanding and solidarity. To clarify your ideas a little, I suggest you watch the video below. It is a cartoon subtitled in Italian. It lasts four minutes and explains how the brain reacts to pain, plus some other exciting things.
"Explainer: what is pain and what is happening when we feel it?" interview with Lorimer Moseley, www.theconversation.com, November 18, 2015