An ingrown toenail is a toenail that has grown into the skin instead of over it. This usually happens to the big toe, but it can also happen to other toes. An ingrown toenail can get infected. It may be painful, red, and swollen, and it may drain pus.
Anyone can get an ingrown toenail, but adults get them more than children do. People who have curved or thick nails are more likely to get an ingrown toenail. This is more common in older adults.