I cut the inside of my thumb deep and has been numb above the cut since it happened. will the nerve repair itself ?

Prob will improve: Depends on the locations of the cut. If it was close to the tip of the finger, and wasn't severe enough to need stitches, everything should heal and the numbness should eventually get better. If it was close to the palm, it's possible that the numbness might not go away. It could take several months to see a difference. A nerve regrows about the thickness of your thumbnail every day.