When you're symptomatic, does it hurt more if you put direct pressure on your patellas ('kneecaps'), pressing them against the end of your femur? Chondromalacia patella from chronic grinding under load will do this; I got mine training for a Quantico vacation (plus a torn meniscus, dammit). Most of the time a dull ache, but every once in a while I'd bump my patella against something and get a screaming stab of pain that nearly made me vomit. Rest (like, REALLY rest), ice, and NSAIDs like hobbsj said, until it's completely gone.
Or you could have Lyme disease.
Hang it up now and take up fly-fishing.
Hope it resolves quickly for ya.