How Soon Will The Ripped Nail Grow Back?

Half my toe nail came off and not clean either.. it look like a thinner layer of where the nail use to be is still there but it looks nasty. i can see spots of blood&& It looks cracked up.it just came off Today 5/15/11- && what happen was my brother stepped on my toe with his shoes on && it lifted my nail and i just pull it off( doesn't really hurt ).My question is how long will it take to grow back?