I feel for you man, I recently hurt my thumb pretty bad- I'm pretty sure it's my trapezium or the "knuckle" of your thumb. Anyways it hurts for me to grip a glass of water with just my left hand much less grip a dumbbell. I feel like I'm getting weaker everyday (been about 3 weeks)
I just want to get back in the gym doing my regular routine, right now when I go it's only cardio or things that don't involve grasping anything (which is unfortunately a LOT)