I think i have a blood boil on my left buttox. it grew as a mass, then became very tender to touch, today it broke the skin and started bleeding. help?

Warm compresses: If it continues to pain or bleed, see a dermatologist.

Visit: That is a part of the body that probably should be seen and reviewed rather than left to conjecture. I would make an appointment with a primary doctor or urgent care doctor first. If requires any additional assistance, an incision and drainage can be performed. If it is smaller than 1-2cm, it may be able to resolve just with time, sitz baths and warm compresses.