Knee Pain!! Please Please Answer!!?

For guard we are doing shoulder rolls and we land with our left leg out straight behind us and our right leg tucked in. When I was doing this yesterday I slammed my left knee into the ground (concrete floor) really hard. I felt a hue rush of pain and it started to swell. My knee is now towards the side a little and it hurts to move it. When I walk I have to limp because I can't put a lot of pressure on it. If I try to move it I hear a pop. What could be wrong?? What do I need to do??