Sorry, as your doctor states, some numbness can be normal after a hair transplant surgery. This is usually discussed and written on your hand out BEFORE the surgery. When there is a small cut on the skin it will disrupt tiny nerves. This will cause numbness. The skin and the nerves eventually heal over time and you will regain sensation. If you are concerned about infection, you would need to see your doctor for an examination.
in general people heal differently. In Some cases it may take longer to heal and take a few months for everything to return to normal.
Any time the skin is cut, anywhere on the body, nerve endings are injured and there is numbness that results for a period of time. Though permanent numbness is extremely rare following a hair transplant, it is common to experience numbness that lasts as long as several weeks to several months until the nerves have a chance to heal. There is no reason to think that the numbness is caused by an infection.
When hair transplants are done, small nerves are cut that can produce a numb feeling for months after the procedure. This will eventually disappear as the nerves that are cut, are small nerves that overlap with healthy ones that will eventually take over the feeling for that area.
Numbness after a procedure can last almost a year in some cases. However, if you are concerned it is a good idea to get a follow up visit with your doctor.