the best way to treat a pressure sore is to prevent it. they are caused by too much and continuous, pressure on an area of the body. usually the butt/coccyx.
they're seen a lot in hospitals and nursing homes because people don't get turned. they're also caused by folks not being cleaned and laying in dirt and wet.

they're very hard to heal and can go down to the bone. very, very painful.
that's the worst case scenario. any areas of reddness on the skin should be CAREFULLY and GENTLY massaged to try to improve circulation and blood flow to the area. i doubt it will come down to any of that for you. stay clean and dry, avoid friction and watch the pressure.