An ingrown toenail occurs when the edge of a toenail grows into the surrounding skin, causing pain, redness, and swelling. This condition often affects the big toe and can result from improper nail trimming, tight footwear, or injury. If left untreated, an ingrown toenail can lead to infection, which may require medical intervention. Treatment options include soaking the foot, wearing loose shoes, or, in severe cases, a minor surgical procedure to remove part of the nail. Proper nail care and footwear choices can help prevent this condition.