Tendon Problem

About a week ago the day AFTER I had a workout (sprinting) the area under my right knee is sore; more specifically the tendon, for sure.

I thought I might be my IT band but its not. I can still sprint 95% plus after I’m warm but when I come home and get cool if I move that leg/knee in certain angles I feel pain.

I’m now stretching 3x a day for about a week but it’s not getting better however it’s not getting worse. What should I do?

Sorry posted this in the wrong forum…