Wow, my cats get irritate w/ one another now and again and hiss, but I don't think any has ever actually had a fight! Fur flying, yup, get that now and again (mostly Mandy and Tommy, who are now separated).

Sounds like a bite, which got infected, nature took over and it healed. Wonder if that will stop the taunting?

Mention it at the vet check, ask what you can do to help the healing if anything, should it happen again.