you have to get all the dirt and things from under the nail and use a nail file to get your smooth end. but with out nail polish the nail wont shine so you might wanna use a clear coat on it.
I tried this trick, it's easy. I know it sounds odd---but try it. Coat the area of your nails that has nail polish onn with another type of nail polish. Leave the polish on for about 10 seconds, then...
Soak your nails in a bowl of hot water for 15-20 minutes. The nail polish can easily be scraped off with your thumb nail. No long nails? Use another pointy edged object!