Martin does wince a little at the unexpected cheek pinch. But it's Nero's forehead suddenly pressed against his, completely apropos of nothing and with everyone watching, that makes Martin's cheeks turn a sudden bright red, and he hasn't even begun to recover by the time Nero starts cackling at his own stupid joke.

(He's mad that Nero doesn't actually smell bad, up close. Somehow Martin was expecting him to positively reek of blood.)

"I- um--" okay Martin does have to pull back a little, breaking full contact with Nero but still staying somewhat in reach. "I-it's nothing, it's- it's f-fine, really. I'm just-- not. Really much of a, uh. A party person? So. This is just a lot of people..."