If you injure your toenail and have active bleeding, seek medical attention immediately. The toenail is at the tip of your toe to protect the underlying structures. If your nail becomes loose, secondary to an injury, this can be a serious condition. You may have a nail bed laceration, or you may have a underlying fracture.
Blood beneath the toenail is one of the most common causes of a toenail becoming loose. It's extremely common in runners. It's very common in tennis players and anyone who's involved in high physical activity.
If you have a loose toenail, I like to keep the toenail in place as long as possible. Sometimes this will require bandaging the toe. I usually recommend to cut the nail back so that it doesn't lift when it hits the shoe.
If you have problems and persistent pain because of the loose toenail, seek medical attention with your podiatrist. They can easily cut the nail back so that it regrows properly.
If you loose your toenail, the nail will regrow back eventually. A toenail grows at a rate of one millimeter per month. So the average great toe will take often up to a year to regrow.