An ingrown toenail (onychocryptosis) is a common condition, usually of the big toe, where the nail cuts into the surrounding nail bed causing an infection and pain.
If you trim your toenails too short, particularly on the sides of your big toes, you may set the stage for an ingrown toenail. Like many people, when you trim your toenails, you may taper the corners so that the nail curves with the shape of your toe. But this technique can cause your toenail to grow into the skin of your toe. The sides of the nail curl down and dig into your skin. An ingrown toenail also can happen if you wear shoes that are too tight or too short. Any of your toenails can get ingrown, but it's most likely with your big toes.