This happened to me all last season, it was just patellar tendonitis. If this is what you have then you're no more likely to get a serious injury, but if you stretch your quad out it should help with the pain.
What I do is find a chair (with a padded seat) that is roughly knee hight, then rest the top of your foot on it and kneel down so your knee dips to the ground, as illustrated by my masterful MS Paint skillz.