I was doing overhead squats with a bar at crossfit and now my thumb is numb and isn't going away, is there something i can to to make it go away?

Nerve trauma: You have put too much pressure for too long on the nerve in your thumb. As this is an acute situation, resting the thumb and making sure there is no pressure on it over time may allow the nerve to recover. Nerves in your fingers are right under the skin and are easily traumatized. Your hands and fingers on them are not meant to bare the full weight of your body. When abused, the hands can rebel.