Please Help ..

I’m wondering what is wrong with my upper thigh muscles. This is how it started.. I haven’t been active for awhile and played football one day. I didn’t stretch or anything. When I went home I was sore and stuff. I thought that was just it because I been through that before. Everything felt fine after 3 days had past. Then I went back out to play again after a week of rest. So I stretched and all, ran a couple of routes but not at full speed. Everything felt fine. Well during the game I ran full speed and I felt something in my upper thigh like a ball like movement inside my upper thigh and it really hurts bad. After that I can’t barely move my leg “right leg”. Well it has been a month now and this only happens to me when I burst into full speed. Can you please tell me what is wrong with me? Any comments are welcome thank you!