Man in question is father of DD's best friend. He is married. He and my DH get on well and socialise occasionally, while all four of us are part of a loose social circle of about 5 couples with kids in same class. I don't consider myself a friend of his wife, though we are friendly, and I probably get on better with him.
I've known him for about four years and he's never been even slightly inappropriate. He's always nice and polite, shows interest but isn't overfamiliar etc etc.
Over the weekend, we were both at a party for a mutual friend. My DH was also there. His wife wasn't. The three of us spent quite a long time talking about various things. This is fairly normal and I didn't think anything of it.
The following day, his DD had stayed over at ours and he came to collect her on his own. My DH wasn't around. We chatted for a bit while waiting for the kids who, as usual, were dragging their feet. Then he said it...
"I just wanted to say you looked beautiful last night,"
I just smiled thanked him. I think that alone might have been alright, but then he said
"Like really beautiful. I've just been thinking about you non-stop."
I think I just made a joke about DH and then shouted the girls to hurry up.
For complete context, there probably is some chemistry between us and probably some mutual attraction but I'd never do anything and, up to that point, neither of us had ever even really flirted with the other. As to how I actually feel about it, I'd probably more err towards being flattered rather than being creeped out.
My dilemma is what I should do. I don't really want to say anything to DH or his wife, but I also don't necessarily want us to have this sort of "secret" between us. I think the answer is that I probably need to tell him he can't say anything like that again, but even that feels a bit of an overreaction to (what is currently) an isolated incident. Interested to see what objective people think.