How do concave nails form?

Different ways: There are few different reasons a nail may get "curved" or concave. Trauma may damage a nail root and deform the shape of the nail. In other cases, a fungal infection may be the culprit of the deformed nail. In some cases, the shape of the nail runs in the family. In other cases, a systemic condition may also influence the shape of a nail. Talk to your doctor for a more complete list.