Ingrowing toe nails are painful and cause inflammation and leave us prone to infection. When the edge of the nail is pressing into the skin it causes every step to hurt. In the early stages when the nail hasn't penetrated the skin it is still uncomfortable though if left can cut into the skin and provide entry for invading organisms. A tight shoe can cause or add to the problem.
If its dealt with early enough then simply keeping on top of it by filing the edge of the nail will stop any future problems. If the nail has penetrated the skin then it needs to be removed and any infection dealt with.
Short term or ongoing treatments involve just keeping the nail away from the skin though there are permanent solutions available including the partial or total removal of the nail and the nail bed from which it grows.