Broken Toenails

Broken toenails can be a very painful injury for dog, especially if the quick has been exposed or broken, since this part of their toe is full of blood vessels and nerve endings. Recently I had two dogs break a toenail within a few days of each other, one of them didn't notice, but the other was severely limping until his injury was taken care of. Breaking of the toenail can be easily prevented by regularly cutting your dog's toenails, but even then it can still happen at any time.
If the outer shell of the nail has been broken back to reveal the quick, there is usually not much you can do other than clean the wound of loose nail fragments and dirt, and bandage the foot if needed. An effective way to bandage the foot is to attach a clean sock at the ankle with gauze, this prevents any dirt from getting in the wound.

Example of broken nail that needs to be cut off

If the nail is broken in half and dangling it will have to be cut off. Unless your dog is very non-reactive to pain and his paws being messed with, I would highly suggest taking him to the vet. We tried cutting our dog's toenail ourselves and it was an impossible task, it ended up taking three vet techs and a muzzle to get the job done.
Broken toenails usually happen because the toenail is too long or brittle. Trimming your dog's nails regularly keeps the quick small and helps prevent this kind of injury from happening. If your dog is outdoors and exposed to rocks and other rugged surfaces a lot, dog booties will also prevent these injuries, along with many other foot and toe injuries.