Suggest Remedy For Pain In Leg & Butt

Two weeks ago I was doing a split.I was down to the ground and while sitting there I heard a very loud pop.I immediately stood up and my leg and butt was in an extreme amount of pain. Since then it has continued to hurt even though I have rested it. The pain is in my buttocks and goes down my leg when I attempt to stretch. What could it be and what should I do?