Yikes, that's no good. Sorry to hear about the discomfort.
Was there any sort of trauma prior to when it started hurting? The area of the knee that you're feeling pain in is exactly where the bone work was done to reposition your kneecap. I do know that some people develop pain due to the screws themselves, and they need to be removed to alleviate.
Basically, you need imaging to start eliminating possibilities. X rays would be the first step, I'd think.
Wishing you the best.