I wouldn't lose too much sleep over it yet. Triggers are fairly bullet-proof as reef fish go, and my blue jaw would get detritus stuck in his slime coat from time to time that would always freak me out when I saw it. Keep an eye on it, and if it spreads, you can start looking seriously toward medications. Even if it IS ich (and I'm not convinced at this point), as long as he's eating well, he should be able to fight it off on his own.
My only suggestion would be to consider upping the QT to 20 or 30 gals if possible in the future - ten's a little small for such an active swimmer. However, moving him now might create more stress than it's worth.
Good luck!