What's the best excuse for a hickey?

He's not my boyfriend, but we've been on a date, and are going out tonight.... the problem is, is i have a really bad hickey on my neck, and am not sure how he'd feel about it. So of course im going to try and hide it as best as i can (make-up, scarf) but if by some chance he finds out... What the hell do i tell him?? I really like this guy and i don't want him to know about it... at all... So anyone got a convincing story?