I think Fred recommends a high wrist grip, so high that you're only holding the bow between your thumb and forefinger. That, in itself, can cause muscle fatigue until you get used to it. Shouldn't cause problems if you loosely grip the riser, but squeezing it could definitely lead to problems.
So called catching the bow as it recoils at the end of the shot shouldn't cause pain, though if it's a new position/action for your fingers, there may be some muscle fatigue there as well. If so, they just may be a bit tender until you get used to it. Could use a wrist sling to find out for sure. If you use a sling, you don't grip the bow at all; it just rests in the V between your thumb and forefinger and at release, the sling catches the bow.