Something Happened to my Knee

What started off as a routine park road run this evening turned into a knee injury. I met up with the group and Mariah, James and I decided to run on the roads, while the rest ran trails. At at mile and a quarter, I suddenly felt sharp pains under my left knee cap. I could not continue. I started walking back and James went back to the Nature Center, got his car and came to get me. I sacrificed some of the ice cooling down my beer and put it on my knee. I'm not sure what is wrong with it. I hope I did not break something. I will try to see my doctor tomorrow. With my upcoming race schedule (scroll to the bottom), it is very frustrating. Thanks to James and Mariah for being so helpful or sorry for messing up your run.