What should you do about a butt muscle strain?

Rest and NSAIDs. Treat all sprains and strains with "rice" - rest, ice, compression, and elevation. Nsaids include Ibuprofen adn naproxyn. Muscle strains can take 6-12 weeks to heal. This is a large muscle so it will probably take closer to 10-12 weeks. Pain in this area may be from piriformis syndrome or sciatica, a sign of a pinched nerve in your back. If symptoms persiste, see a doctor.
Rest, ice, Phys Tx. A myriad of muscles are included in that area: gluteus minimus, medius and maximus, hamstring muscle/tendons to name a few. Rest, ice, nsaids and physical therapy may all help diminish the acute pain and discomfort from a muscle strain.