How long does it take for a piece of a fingernail to grow back?

I was shaving my legs and the razor somehow cut my nail. it is my thumb nail and it is like a little piece that was partially sliced. it kinda looks like a bracket ) with one side slightly indented. I have not ripped that small piece of because it hurts. I can rip it off though. should i leave it like this (no ripping) or should i remove the piece? how long will it take for this small piece to grow back?