I'm not trying to be funny..but if it's about to come off then just clip it off as far as you can. If you just let it hang it will end up getting infected..Clean it with peroxide and file it down as far as you can stand it. Then get some Vicks Vapor rub...(you know the shit you put on your chest) and put it on the Toe and Nail bed...Again I am not bullshitin' you...The Vicks kills fungus..and is the best thing for athlete's feet.
If your toenail is coming off it's because of a fungus infection in the toe..
bobv