What is nociceptive pain?
When you sprain your ankle, you damage some of your tissues (such as ligaments), as can be seen from the fact that your ankle swells up. Damaged tissue releases all kinds of substances that activate tiny receptors at the ends of the nerves in the skin and around the ankle joint, known as nociceptors. The activated receptors send signals (electrical impulses) through the nerves to the spinal cord. From there, they are passed on to the brain, giving you a sensation of pain.
Nociceptive pain can also result from other types of inflammation (for example, rheumatism), or after surgery, which of course also causes tissue damage.