Clear nail polish over and over again on a daily basis.
Tie it off with a piece of string or dental floss very tightly. It'll turn black and fall off. Ew, I know.
I've heard Vick's Vaporub works, but it didn't for me.
Or, if it's little, sterilize a nail clipper or tweezers and clip or yank it off. It'll only hurt for a second.
Nan