I had this issue, but was finding my hands were so large that I was damn bear overlapping my fingers on themselves around the bat.
I grabbed these Grip-N-Rip handle grips (one symmetrical original one, and one called the "trigger" which has two finger slots and a tapered palm side) off of Amazon for a few bucks a piece for my bats, I now have a more comfortable grip, and the butt no longer rests against my hand.
They've been durable through two seasons, and go on easily with a little soap water. Avoid adhesion on the inside for the tapered grip, you will want to rotate which part of your barrel you contact with everyone couple months at most.
Hope this helps you too, I spent a solid 10 years of my "beer-career" with hand pains.
Batting gloves are also an option if you're not yet using any (your hand may just be irritated slightly from it being a soft area of skin)
Cheers