Knee bent wrong way now

Patient: When I was playing soccer somebody fell into my right knee and it bent backwards a bit. I couldnt put any weight on it for about 20-30 seconds then i gould but it still hurt. Whenever i put any weight on it while it is locked or straight there is a sharp pain inside my knee and my leg sometimes gives out. I can still walk fine though but im scared to run just in case i injure it further. Ive searched a while and havnt found anybody with the same thing. Can you help tell me what this is and what to do?

Symptoms: Dull aching pain in knee when not in use, sharp sudden pain when leg is locked or straight then leg usually gives out