I would watch the nail closely. Slim chance of infection but I wouldn't start him on antibiotics just yet ;0)
Go out and get a bottle of Kwik Stop. It's the powder form of the styptic pencil. It's got iodine in it that will disinfect the cut as well as stop the bleeding. Can be used on nails, small cuts(like paper cuts), but it does burn.
I also suggest investing in a Dremel! Last dog I did nails on with a nail clipper, I must have quicked her on all four feet, at least one if not two nails each. She was stoic and didn't even flinch-didn't notice till I saw blood on the grooming table. The dremels with a 60 grit sanding drum are much easier to use, never had one nail bleed from getting too close and the nail is smooth when done. Here's a good link for info on the dremel and nails:
How to Dremel Dog Nails @ DoberDawn.com