“How long does hand nerve damage take to heal?”

That depends upon what you mean by "nerve damage." If you are referring to a nerve laceration that was repaired surgically, this really depends upon the specific nerve lacerated and how close it was lacerated to the hand. That being said, a general rule is that it takes about 3 weeks for a nerve to begin to regenerate after it is surgically repaired or injured and then it regenerates at an average of 1 millimeter per day. Good luck.