I saw a thread somewhere in here where a couple of people had labyrinth fish that had some sort of pimple type thing on their heads that, at some point, burst open. The fish ended up covered in some sort of fungal growth. #1, don't use Melafix (I think that's the brand.) That ended up killing one of the fish. It's got something in it that doesn't agree with labyrinth fish (which guorami are part of) I'd have a quarantine tank ready and a supply of a good, labyrinth fish-safe anti-fungal med ready. (If you
betta people could toss out a few names for Andiuk, that would be great. I'll need them, too, as I'll have a betta soon)
Not trying to scare you, but what happened to the others suggested that, once things went really bad, the fish needed immediate treatment. I'm not trying to scare you or worry you excessively, but I want you and your fish to have as much of a chance as possible.

I hope I'm wrong. It could just be a parasite, a damaged scale, or a benign viral infection (pretty much a fishy version of a pimple).