During the surgery that I had on my jaw and chin, there were nerves that were cut or perhaps just damaged that had to do with feeling and sensation around my lower lip and chin, but did not control movement. There was numbness for a long time, which was then replaced with a pins and needles sensation and being ultra sensitive to hot and cold. Finally, my sensation returned to normal. It took years before normal sensation returned.
I'm not sure this is the kind of nerve damage your friend's doctor was talking about, but that is the kind I had.
Susan