[WhitehartFB]

Sore fingers can also be down to tension in the fingers and the forcing of the fingers open to release the string. If you just relax the fingers the string will just move them aside but when there is tension the string is forced around the fingers.

Another cause is not going deep enough with the finger placement of the string. Some archers hold the string on the tips of the fingers believing this leads to a cleaner release, in fact it's the opposite.