Nails with black lines and vertical stripes are usually a sign of a nevus of the nail, and the treatment is usually surgical removal.
Onychomycotic nevus is a pigmented change caused by a common pigmented nevus that grows below the nail plate, manifesting as a black band several millimeters wide on the nail, spreading from the root of the nail to the tip of the nail.
Naevus of nail is not sensitive to drugs and conventional treatment is less effective. Surgical excision is usually done by first removing the nail with an instrument, then making a shuttle-shaped incision around the mole, removing the mole tissue completely and then sewing it up.
After the surgery, keep the area dry, breathable and clean, do not touch water or dust and other impurities, and avoid pressure or bumping into the surgical site. Before recovery, it is recommended to have a light diet, less spicy, greasy and stimulating food, and no alcohol.
Surgery should be performed in the dermatology department of a regular hospital, operated by a professional physician.