TheFapI have the same thing right now with track. Its most likely your SI joint. Try not doing to much on it for a week. Ice it a lot. And if you do ski or something heat it before and ice it after. Also stretch like twice a day. Your leg is all connected so loosening it all up will help. Good luck man. It fucking sucks
I've had a sprained SI joint for 3 months now. Not much to do about it unfortunately. Heat/ice and rest it and it'll get back to normal soon enough. Just in the past week and a half that I have stopped skiing it's gotten loads better.