Knee pain after squatting motion

Hi,

I ride a BMX bike and for several years I have been doing a trick that involves jumping back onto the bike. My left foot lands on the pedal and my right foot lands on the frame, carrying most of my weight. I'm pretty tall (6'6", I know I shouldn't be on a BMX), so this means my right knee gets bent quite far back as I land. I noticed that it was starting to hurt when I did this a few months ago so I pretty much stopped doing the trick entirely, as I'm 27 years old and I'm aware that I could really save problems up for myself further down the line. Yesterday, due to nothing I can pinpoint, it started hurting all the time when I pedal (you are stood up all the time when pedalling a BMX). I was literally riding in the morning at one skatepark, didn't get hurt or notice anything wrong, then I pedalled across town to another one and it had suddenly started hurting. It is not agony but it basically hurts in the same way that it used to when I did the trick that I suspect started it off, as I sit here now it feels warm and tingly, but not in a good way. Any advice will be much appreciated!