I'm actually experiencing something very similar right now. Its in my left hand though. I've been trying to work around it and have discovered that not holding a tight hookgrip overhead and letting my thumb joint collapse outside of my hand cause a the pain. A doctor suggested I had strained a ligament in my hand. If I focus on keeping a tight hook grip the pain is minimal, but as weights get heavier it becomes harder to do that. Straps can help sometimes too.
I'd be interested in hearing if/how the hand issue resolved itself and what you did. I know this is an old thread but I'm new here.