[Auballagh]

I dunno, besides the interesting 'chin bump' your Keyhole actually looks to be in the peak of health. Even the protruding area shows no sign of being irritated or something. And, I'm guessing there is nothing pushing up inside it's mouth from the bump that causes problems with eating or anything, right?
Someone else may offer something about that bump. But for me, I'd say that Cichlid looks quite healthy and normal.

 

[Auballagh]

Totally agree. Who knows how your Keyhole got that bump? Maybe an old battle wound from when it was much smaller? Or, it could possibly be something that it was just born with. Your Cichlid looks very good, and is swimming well in the video. And, if its as you say, and is eating normally? Well, four weeks is a good, long quarantine period.
I'd say it was time for that one to go back into circulation! :thumb: