This is not unusual- it can take several months for scalp sensation to return to normal after a transplant procedure.
It is quite common to have numbness in the scalp after a hair transplant surgery. For the first little bit you may even experience occasional sharp pain in the donor area. This is to be expected as the nerves that were damaged in the procedure are healing. Just be sure to let your doctor know so that they can do a proper assessment and make sure that everything is healing properly.