Extreme sudden groin pain

Patient: I was rock climbing the other day. I was on the wall and all of a sudden I got an intense feeling of pain in the inside of upper thigh, near my pelvis. My leg was totally seized. After about 30 seconds the intensity died. Now, like 4 days after, with only mild discomfort in my groin, i started to run up the stairs and again this searing pain that knocked me down and left my leg totally useless for 30 seconds again. The pain almost felt like a burning sensation. It was really unbearable. What is wrong with my grion?