Well he should eventually get to a point where you don't have to do anything to get him to stop. But something a simple as a tap and a clear command should be enough to get him to stop while you're still training him. You just have to be consistent and firm with him. It's like teaching a kid...at least I assume that's what it's like. But it sounds like you landed a reasonable one, so you should be fine.

[He's been a kid, but he's never actually raised one before so...]

Ahaaa...yeah. Is it a malicious bite though? Or just like...a playful nibble?