maybe. if the tooth did not penetrate through the skin of the outside or the vermillion border (the pinkish part of the outer lip that meets the skin) has not been disrupted there may be little that can be done. most minor injuries of the mucosa side of the lip will quickly heal. i assume the tooth is fine. laceration repairs should be done within 8 hours of the injury so make your decision relatively quickly. if you are having any doubts whether he will need a stitch or two take your son to an urgent care facility for a hands-on evaluation. since i am unable to see the injury i can only offer you this general advice.
my 3 year old son fell and his tooth went through his bottom lip. do i need to take him in?