Whether you want to treat this on your own or get help from a professional, a good starting point is to gain some understanding of what is causing the pain. If you have severe pain in one side of your buttocks, you have narrowed the field slightly. If it is only there when you stretch or sit, you have narrowed it further. It is most likely muscle, nerve, joint or some combination of the three.
Muscle injuries are called strains and occur when the fibers in a muscle tear due to over stress. Pain may come on quickly or slowly but you can usually tie the onset to some activity. Most sub-acute muscle pain is more dull and achy rather than sharp. Treatment consists of rest, application of ice for 10 to 15 minutes several times a day, and pain medications like ibuprofen. The pain should resolve in less than two weeks.
Irritation of a nerve is usually described as a sharp pain. In the buttocks, the most common nerve to be irritated is the sciatic nerve. It is a large nerve that comes out of your lower spine and travels through the buttocks on its way down your leg. It can be irritated by a degenerative or bulging disc in the spine, inflammation of the sacroiliac joint, or the piriformis muscle right under your hip pocket. Use ice over the pain and over the spine to reduce any inflammation. A gentle stretching program for the legs and lower back will help.
Irritation of the sciatic nerve can occur in joints at the spinal or sacroiliac levels. There are five spinal nerve roots that contribute to the sciatic nerve and irritation of any one of them can cause sharp pain. Dics herniations, protrusions or bulges can be the problem. You may also get pain from a sprain of the hip joint or the hip bursa. If you feel this may be your problem, talk to your doctor, chiropractor or physical therapist.
Unfortunately, most nerve and joint problems also have a muscle component because your body will use the muscles to help keep the injured joint or nerve from further damage. Clear identification of the cause may not be simple. If you have tried a couple of weeks of conservative care with rest, ice and over the counter pain medications and are still having pain, you should see your doctor to investigate the problem further.