Small pits on the nails are caused by ringworm of the nails, lichen planus, nail dystrophy and other factors. 1. Ringworm of the nails: ringworm of the nails is a disease caused by dermatophytes invading the undernails and nail plate, due to the nails being infected by fungi, which in turn will cause unevenness, easy to break, and some of them appear to have small pits. 2. Nail lichen planus: Nail lichen planus is a chronic skin disease, which may be caused by mental stress, medication, heredity, infection and other triggers, and may be manifested as thickening of the nail plate, unevenness, roughness and other symptoms in the clinic. 3. Nail dystrophy: the cause of nail dystrophy is complex, may be related to the lack of trace elements, but also may be caused by long-term chemical stimulation, which will appear on the nails with the phenomenon of sunken pits. It is recommended to go to the regular hospital for examination, the doctor will be based on clinical symptoms to give judgment, clear causes and timely symptomatic treatment.