A dimple is a small indentation in a surface. A dimple on your cheek is cute, but a dimple on your car door is not so cute.
A dimple can be an imperfection or tiny dent, but it's often a little cleft in a person's cheek or chin. People whose dimples show when they smile are particularly charming, and a dimpled chin is often considered quite handsome. One theory of the word's origin is that it meant "pothole" in Old English, from a Proto-Germanic root.