If you have to hide a part of you then either you are insecure about who you are or insecure about what the other person may think.
Have an open conversation about the surgery and let him know that you are self conscious and wait on his response. His response will let you know if you are the summation of a scar or of the qualities that make you a whole person. You should know that you are more than a scar and based on how he reacts, keep him or let him go.
He may say that the scar does not make a difference but if you have seen him scringe at anything out of the ordinary, that will give you a clue to his sincerity. Hopes this helps.