This has been a recurring problem for years now, but I continue to have issues with my thumb. On the inside part on my knuckle I get a callus and almost always has a blister underneath it. Fluid is inside and if I can drain it it feels better, but I know that this is not something that should happen. I have tried many different things to help it. I don't squeeze the ball as badly as I used to and I can tell that makes a difference. I have changed pitches, and that has helped too. What other suggestions can you make?