Which condition is typically characterized by a nail that has grown into the surrounding skin?

Onychocryptosis, commonly known as an ingrown toenail, is characterized by the nail growing into the surrounding skin. This condition often affects the toes, especially the big toe, and can lead to pain, swelling, and potential infection if left untreated. Ingrown toenails occur when the edges or corners of the nail grow into the soft tissue of the toe, causing discomfort and sometimes requiring medical intervention.

In contrast, onychomycosis refers to a fungal infection of the nail, which can cause thickening, discoloration, and separation of the nail from the nail bed, but does not involve the nail growing into the skin. Onychophagy is the practice of nail biting, which leads to nail damage and can cause infections but again does not involve the nail growing into the skin. Onychia, on the other hand, refers to the inflammation of the nail matrix and can result in nail loss but is not related to the nail penetrating the surrounding skin. Therefore, onychocryptosis accurately describes the condition in which the nail has grown into the skin.