Knee Pain--Race on Saturday!

Hi all,

I've been a lurker for awhile and I have my first Olympic tri on the 17th! I was really excited but Monday I was on a run and tweaked something in my knee. It was a group run and I did not get to stretch before hand. I had sharp pain on the outside of my right knee and was unable to walk for about 20 seconds before it felt better and I was able to finish my run. I didn't exercise on Tuesday but swam with no issues, just some tightness/soreness on Weds. Now's its Sunday and the pain has turned into a constant slight ache (maybe just in my head?). I feel pressure in my knee going up and down stairs and in general my knee feels weak. The pain is more centralized than on the right side of knee where I had the initial pain.  

What should I do? I really want to race on Saturday (spent Feb-May training, bought a bike, excited as hell) and I am ok with a bit of pain but I also do not want to ruin my knee more seriously. 

Thanks