Never try to train through joint pain. You have a medical/health related problem and until you deal with that you will not be able to train to full effectiveness and may exacerbate the issue resulting in more lost training time in the future.
Pain lateral to the patella and especially below the patella can often be caused by a tight IT band. This is really common among runners. The IT band attaches to the tibia just below the knee cap and so the pain can feel like patella tendonitis when in fact the problem is far removed from the knee itself. The origin of the IT band is in the lateral hip area just below the iliac crest. Aggressively rolling out this area and the full lateral side of the thigh with a lacrosse ball or a foam roller several times a day for a few days will usually give relief to this kind of knee pain (if this is the source of it). Once you get on top of this issue you’ll want to do preventive rolling. If when you roll the IT band (or any muscle) it is excruciatingly painful then you can be pretty sure you have found the problem.
In my experience tight IT bands are the most common cause of knee pain in runners.
I hope this helps.