Had the same thing, and now have had 3 months off and counting. I didn't think much of it, but after several weeks the pain got too great to run on and I've been off ever since. Looking back I should have worked on quad, ITB and hamstring flexibility and ice as much as possible.
There are quad stretches where you are extended at the hip, which stretches the upper portion of your quad to spare the sore area on your knee. Try those maybe.