Your best bet is to just take a break from holding a mouse as much as you can until the pain is pretty much gone whilst resting and only crops up when you have to use your wrist. Then try and switch grips. If you don't take a break to see what your wrist is like whilst not using your mouse, it will continue the stress you're already putting on it as well as you won't be able to tell if its an improvement or not.
Anyways I use palm grip and it doesn't help with my rsi so I wouldn't expect it to change anything. Just play games in moderation and don't play for too long in one session so you can rest your wrist.