Hi, I Am Having Some Pain Behind The Knees. I

Hi, I am having some pain behind the knees. I am still able to walk and run with no pain. There is only some pain/discomfort when I perform certain movements. For example, if I am sitting down on a rolling chair, and with my legs bent, I push myself forward, I feel some pain under my knees. I've been having this pain for about 2 months or so.
Is this pain any cause for alarm? I'm trying to determine if I should seek medical help or if the pain will go away eventually.