No, do NOT use peroxide. It damages the tissues and actually hinders healing. It went out of favor with the medical establishment many years ago.
First, clean it with a very dilute solution of Hibiclens, and rinse well. The active ingredient in Hibiclens is chlorhexidine, so if you can't find Hibiclens, you may be able to find a substitute. Rinse the wound well.
Does it look more like a scratch, or a puncture wound? If it's a shallow scratch, cleaning it may be all you need to do. If it's deeper, you need to keep a VERY close eye out for any signs of infection -- redness, swelling, tenderness, oozing, pain, etc. If you see that, he MUST see a good vet for a piggy-safe antibiotic. If the pig CANNOT reach the area with his tongue when he's grooming himself, you can put a tiny amount of a triple antibiotic cream on it. Use a q-tip, and rub it in well. But if the pig can lick the area, don't do this, because the cream has several compounds that are dangerous to guinea pigs.
You need to put back some money for vet visits. It's not fair to an animal to keep it and not be able to provide for its medical needs. Many people on this board regularly put money in a pig emergency fund for just such occasions as this. You also need to find the closest good exotic vet -- small animal (dog and cat) vets are not equipped to treat guinea pigs, and many will refuse to see them because they're not trained in their care.
