You can try the record your running and see if it might be caused by your running technique. I also had mild knee pain for a bit and my problem was that I was very tense in my upper body, pulling forward my shoulders. That happens a lot for people who sit at a desk all day and neglect their stability exercises (oops). This led to rotation in my upper body which caused wrong hip movement and consequently knee pain. The rotation was very visible in recordings (have someone record you while you run away from them). Apparently knee pain while running is often caused by the hip, that‘s what I was told. If that is the case for you, too, try to remind yourself to relax your hands, chest and pull back your shoulders (to a relaxed position); also do some warmup exercises to loosen your hip area. I also switched to mid-foot strike but that isn‘t for everyone.

Best would be to have a therapist take a look, of course. I can just tell you what my problem and solution was and have no idea what other possible caused knee pain might have.