Does anyone here have a Beta fish or know anything about them?  

Hmm, that's a new one on me. I'd call up the pet store and ask what they have, and what they'd suggest. There are various water additives that help with skin conditions, and one of these may also be good for protection while the scratch heals. (Is there anything in the tank for him to get scratched on?) If they're unsure, try calling the vet - there's probably a trade off between keeping the water very clean and not moving him very often.

My guess would be, if he's in a very small tank, to move him to a larger one so the water stays cleaner longer. I hope he's ok - lots of fish survive attacks in the wild so hopefully he bounces right back (though maybe with an interesting scar ;])