If he didn't make sure to check to see if the head came out then it's possible it will grow back. He should check that area regularly to see if anything is growing back. He might also want to try to identify what species of tick it is as some carry serious diseases and it would help to know what you might have to watch out for. Like for example deer ticks are known for spreading Lyme disease and one of the classic early signs is a round shaped persistent rash that spreads outward and sometimes causes a "bullseye" shape on the skin. In this stage the bacteria from the tick, causing the problem is still fairly localized and therefore treatment tends to be more successful then if it spreads throughout the body, as it will do if not caught quickly.
