Cortisone Acetate and graph

I am 21 years old.1 year ago I had an ACL transplant. I worked hard to get my knee back to strength. It felt good except slight clicking in my knee near the lateral meniscus. I had a second MRI and it showed the new ACL graph healed proper. My doctor gave me a cortisone shot in my knee where the clicking was to see if maybe it would help. I do a lot of strength training and that week it felt better than ever. I went to play paint ball on the weekend like I always do and after sliding on my knees for a few hours (even with knee pads) it started to hurt worse then ever. Then nest day( witch is now) my knee is swollen and hurts to even walk on it. It hasn't swollen up for over 7 months. I don't know if the cortisone shot was such a good idea.