First I would make sure he is on a substrate that won't irritate the wound, like a towel or newspaper. Next, I would rinse the wound out with a 50/50 Hydrogen Peroxide mix. After that I would rinse the wound again with a dilute nolvasan solution. I don't know where you can buy nolvasan (I'm a vet tech and I get it from work) but a betadine solution would work as well (though be a bit messier). I'm not sure what other ppl use, since I have access to medical products. Is nolvasan sold to the public regularly? I'd guess that you could contact an emergency clinic and they would sell you some, I know my place would.
You said the wound was the size of a dime, does that mean it's circular? If it is, that sounds more like a scrape than a cut and I would check his enclosure for places where he can get stuck or anything protruding that would scrape him that badly.
When people ask me if i'm a cat person or a dog person I tell them, "I'm a snake person"!