OP
Try the following buy some zinc oxide tape place the first piece of tape under your knee cap stick it to your skin (press hard!) then depending on leg pull it tight and upward and the stick it against the side of your leg. Then place another piece of tape below the first (just touching) then once again pull it up on a diagonal and stick it to the side of your leg.
Basically your pulling the skin etc to the outer side of your bad leg. If this eases it you have the same problem I have and need phsyio. It’s basically the tendon in your leg not running straight over you knee cap.
When I first got it I was out on a ride and could hardly make it back it’s like some one sticking a knife into your knee cap and VERY pain full.
It took 3 doctors appointments and 2 NHS physios before I found someone who knew what the issue was (a knee specialist Physio). Then 6 months of physio.
I now HAVE to ride my bike if I don’t within 2 weeks it starts to come back.
It’s cause by a mussel mismatch and the mussels in your thighs need strengthening in order to pull the tendon back straight.
*****NOTE I’M NOT A DOCTOR OR PHYSIO. So get professional advice.*****