An ingrown nail is when the nail is growing into the skin at the border and pierces the skin.

Ingrown nails can sometimes be caused by footwear being too tight.

Increased pressure at the nail and skin can cause the skin to be fragile.

If a nail is cut incorrectly, it can pierce into the skin and cause an ingrown nail. 

This can cause a large amount of pain and also may lead to an infection.