The mother was counseled that the dimple probably would not go away, but that it may become less noticeable as the child grew and was unlikely to cause any problem. Discussion Skin dimples over the spine commonly referred to as sacral dimples are common minor congenital anomalies, estimated to occur in 3-8% of children.
https://pediatriceducation.org/2009/07/20/does-this-sacral-dimple-need-to-be-evaluated/