What Causes Hip Pain After Falling Down During Pregnancy?

Im 7 months pregnant and fell down half a flight of stairs (about 7 or 8 stairs) on my butt. My left hip hurts when i put pressure on my right leg to walk. It also hurts to sit and lay down on the left side. Baby is fine. Moving around normal. I work seven hours straight on my feet. What could be the problem with my hip?