Hello, Thank you for your query. Muscle injury is usually associated with local inflammation and swelling. This can take many days to heal, even weeks especially is there is recurring friction or pressure on the area. In your case, sitting adds pressure and hence increases inflammation. It also reduces blood supply, that when you stand up after a while, the blood gushing to the area causes throbbing pain. I recommend: -avoid sitting for too long. If you can t keep a thick soft cushion or pillow under your buttocks to minimize pressure on the injured area. -keep changing position. -apply warm compresses to the area for about 10-15 minutes or take a warm shower. Then apply anti inflammatory gels (diclofenac) over the entire area. Apply gently and in circular motion. After an hour apply ice pack to reduce the inflammation. Do this thrice a day. If you feel any hard swelling or a bruise is persistent, or if the above measures don t provide at least 50% relief in 5 days, see your physician to see if there is any bone injury. Hope this helps and you feel better. Please let me know if there is anything else I can help you with. Wish you good health