How does pain develop

Pain, our body's alarm system, is both a tangible and an emotional experience. A person’s pain threshold, each individual’s ability to feel and tolerate pain, varies according to each situation and person. Research shows that one's psychological state plays a big part in how one experiences pain: for instance, people report that injections hurt less when they did not see the needle coming than when they actually saw it puncture their skin. Furthermore, if we get hurt while practicing an enjoyable sport or activity, we will likely not feel much pain right then, even if in cases of severe injury. We've all heard of the football player who makes the touchdown with a sprained ankle or the ballet dancer who finishes the show with a damaged ankle. Neither felt a twinge, until later.
Our body has pain receptors scattered throughout its cells-when stimulated, these receptors send signals to the brain that to produce what we call "pain". While unpleasant, pain is actually our body's way of letting us know in no uncertain terms that attention needs to be paid. Pain results from a wide range of stimuli: physical, chemical or thermal. When a tissue is sufficiently stimulated, it locally produces substances called prostaglandins, which produce inflammation. This results in a rise in temperature and swelling of the affected area, and increases nerve sensitivity. By inhibiting prostaglandin production and having anti-inflammatory and analgesic properties, Aspirin® is a highly effective pain-reliever.