An ingrown toenail happens when the edges or corners of the nail grow into the skin next to the nail and break the skin. It is a common condition, and it can be painful, causing swelling, redness, and sometimes infection. It usually affects the big toe, either on one or both sides of the toe. When the nail pierces the skin, bacteria can enter the wound. This can result in infection. The area affected becomes red, swollen, warm, and painful. There may be bleeding and pus. If you suspect that you may have an ingrowing toenail, it is important to keep the area clean and dry to prevent infection. Anyone with symptoms of infection should seek medical help, either with a primary care physician, orthopedic surgeon, or a foot care specialist known as a podiatrist.