Brian K,
Soreness in your index finger on the inside is either caused by you putting to much downward pressure on the nock.......or as you stated, the string pinching your finger down into the nock.
I've been there.......and done that. That is the main reason that I switched to three-under. After switching though......my release was cleaner and I just stuck with it and no longer have even the slightest bit of tenderness on any of my fingers.
If I shoot shorter length bows a bunch (60" and under) it causes a callous on my ringfinger, but it only happens with shorter bows.
Oh, and I shoot with a deep hook and draw a true 29 3/4" also.
Winterhawk1960