The Hand-X Band Grip Strength Trainer was a game-changer for my achy elbows. It’s basically a resistance band that you use to strengthen your grip in the opposite direction. The company sent me a bunch of these when they saw that I was using a strap around my forearm to combat elbow pain.
And it actually worked!
Recommendation: ease your way up. I couldn’t even straighten my fingers at first and I think trying to force that might’ve caused a whole different problem. So consider starting conservatively with just a few reps at a time. And try their lighter versions before graduating to the heavier resistance.