Knee is the worst thing to fuck up. My knee is pretty fucked, I smashed it on a trambouline(?), it bended inwards. Happened like a year ago, and it's still not alright. I suspect it never will be. all I can tell you is to go see the doctor, get a scan or summing. Really, if anything's really wrong, you wanna know. Also, as someone said, keep it elevated for the first 2 weeks, just 'til the swelling's off. Then, if something's really fucked, try to train the muscles around it as often as you can, just so they can support it. Mostly when an injury occurs to the knee, it weakens it in such a way that there's a higher chance for it to happen again. You wanna strenghen your knee to counter that.
My sympaties, I know what it's like.