Ingrown nails are caused when the nail is incurvated (turned in) and penetrates the skin. The improper trimming of the nails, tight shoes, or injury to the nail can cause ingrown toenails to worsen. Early and mild ingrown nails are slightly painful and red. Later, more severe cases result in red, swollen nail boarders which might pus over. Partial removal of the corner of the nail usually gives prompt relief. If this condition becomes chronic, then permanent nail removal of the corner might be suggested.