Had a similar pain during the same, turned out to be overly tight anterior leg muscles. Try this:
1) Pay Attention to exercise form, and other mobility aspects above and below the knee.
2) Smash your quads & hip flexors (and/or ITB & adductors if need be). Spend 8:00 per leg, twice a day.
Correct Quad Smash Technique:
3) Couch/wall stretch like it’s your job. I’m talking like at least 3 times per day, at 2:00 per leg (6:00 per leg / per day). This is the most important in conjunction with #1.*** If this is painful, your anterior leg is too tight.
4) Smash and stretch your calves – make sure you have full ankle range of motion. Also, anterior tibialis: use a tennis ball, or lax ball and start to “peel” it off your tibia. Clean up the fascia right below the knee.
5) Voodoo band your high hip, mid quad, suprapellar pouch, and high calf / right below your patella. Perform squats (good form) and calf raises / stretches while in the bands for ~ 20 reps. Feed you knee joint some slack by voodooing above and below the knee.
How To Make Your Own Voodoo Bands: