So every injury is different for every person. When I first tried to do the festive500 in 2016 I gave myself an overuse injury that took 6 months to recover from, went to doc, got xrays, pt, bike fit, etc.
I definitely recommend (if you have good health insurance where PT is included) to get some Physical Therapy. Sometimes one can get lucky and learn some interesting stuff. 
There are three primary things I noticed in my recovery.
- Ankle Dorsiflexion. I have a very high arch but relatively bad ankle dorsiflexion, leading to pressure on the front of the knee. ← doctor mentioned that.
- relatively weak gluteus medius, leading to very tight IT band. ← pt mentioned that.
- Tight Psoas (work in a chair all day, ride a bike bent forward). ← I noticed that.
So, things you might try.
- roll out your calves (check other ankle dorsiflexion things, most of my issue was associated to calves)
- Roll out your IT band (do clamshells, I never end up doing these, but I probably should)
- find ways to stretch the hip flexor, psoas muscles ( I use what amounts to a lunge where I extend the back leg and keep my chest up. Something like a Warrior pose)
Funny story, so I had all this pain and I was playing pinball and had one leg forward and one leg back and I noticed my knee pain went down afterward. Sometimes in the morning while making breakfast I’d lean on the counter to keep my torso upright and extend one leg back to stretch out the hip/psoas.
I’ve also massaged my psoas (which isn’t easy or pleasant).
Again, n=1. Everyone is different. But none of the things I’ve suggested should do you any harm if you give them a try.
I also returned to riding by jumping on zwift and pedaling until I felt any pain, and then immediately stopping. I think the best #notADoctor advice I can give you is, if it hurts, don’t do it.
Good luck.