I Hit My Knee About A Week Ago And Instantly

I hit my knee about a week ago and instantly had a bump and bruising with very low tolerance to standing on it due to the pain. Well by the next day the bump had grown to almost a golf ball size lump with severe bruising. I used ice compresses and they helped with the swelling. The pain even almost went away. But a few days later the pain returned along with some swelling. It hurts but I can move my leg ankle and toes. What could be wrong?