Oh dear, Ianto! That close encounter must have stirred something he wasn't expecting, presumably he's not accustomed to finding men attractive!

I'm sure Jack doesn't have that problem, but he's aware that Ianto's a little unsettled, so he won't make a move. He'll just wait and see what happens and behave accordingly while Ianto figures out what he's feeling and what it means. I hope Jack's patient and can wait!