An ingrown toenail is caused by a nail spicule grownig into the skin.
This piece of nail must be removed in order for the nail to heal. In many cases the spicule is in the back or middle of the nail border. If this is the case it would be very difficult and painful for you to try and remove yourself. You can even make it worse if the you do not get out all of the nail spicule. See a podiatrist.