Poor doggie!!! It's hard to tell...if it's a toe break-could they even set it? I dunno.
As others have said, if it's a split toenail (or even a lost toenail) that's easy-just keep it really clean.
For that kind of thing -where it's kind of hard to see, I would soak in peroxide. That's what we did when Mikey split his webbing between his toes. (whenever he sees that cup now, he goes to sit on the couch out of habit); We'd fill a cup with peroxide and just dip his whole foot in there. (You can buy JUGS of peroxide for cheap)
We soaked it in peroxide then applied pancur (but neosporin is perfect too!) and then wrapped it up in vet wrap to keep it clean.
I also made a sock type thing out of canvas -elastic kept it on pretty well-so that he could go outside without getting it filthy.
Crio had used some other type of cleaner-and iodine something or other. That may be better. Hopefully she jumps in and says what it is. Peroxide is super disinfectant but it does take away new skin cells as well as dead ones, so it can take longer to heal.
Also-go buy a cone (e collar) if your dog is licking it; he can keep it open and get it pretty dirty doing that