What will help with my knee pain?

Patient: 2 months ago I hurt my knee when. I took a nasty fall. They said it was a contusion. About 2 weeks ago I fell on it again and now I wake up in the middle of the night unable to unlock my knee and in severe pain. What is. going on and is there anything other than going back to the drs I can do? It also happens when I sit certain ways or when I am trying to stand up. I can’t really afford to go back to the dr again. Please help me.