Fingernail torn off accidentally.?

I was messing around with some friends and I pushed open a window and it slid open really fast and my fingers got caught between the panes and the skin connecting the nail and tissue was torn. The nail is still attached around the cuticle. I want to just pull the nail off and get it over with but someone told me that if the nail came completely off, a new nail wouldn't grow back. Would it be better to simply leave it alone and try to let the tissue reattach itself to the nail (I don't know if that's possible or not), or should i pull it off.