I had the same pain; turned out to be tendonitis.
I dropped the ring finger span by 1/8", making both finger spans equal. (5" & 5 1/8" to 5" and 5") This made the grip feel loose and uncoordinated.
I had to compensate for this by tucking my pinky, only up to the first joint. Since the tendons for the ring finger and the pinky work together, this tightened my grip just barely enough to make the grip now feel comfortable again.
Been doing this for 12 - 15 years or so now. I carry a set of Steel Fingers with me, just in case, the pain re-occurs, but it hasn't.
Until you have this (dropped ring finger) done or some other fix to stop this pain, I strongly suggest using a set of Steel fingers to reduce the potential for ongoing or permanent injury.
http://steelfingers.com/FYI See a doctor and make sure of the cause of the pain, before doing anything else!! Unless you're sure of the cause, any cure is just a stab in the dark.