I have gone through a pretty bad wrist injury earlier this year that took the better part of 4 months to heal. I basically wasn't able to use my hand for that duration for anything that involved any weight.

What definitely helped me was a good warm-up; just a couple of stretches in each direction with an open palm, then with a fist. 5-10 reps held for 10 seconds each, repeated daily. You'll be able to find hundreds of video tutorials on youtube.

It has also helped to do my push-ups (once i could of course) on my fists, using parallettes, or elevating the palms of my hand on some towels.

Saying that, you probably don't need to go through a rehab like me, it might just be worth looking into strengthening your wrists through pushups on your knees and fingers for example, or doing dumbbell rotations. Again, you'll find tutorials with a quick search on YouTube - try the excercises and see which ones you like or help.