What was that kind of signal? Was he just being nice?

My friend got something in het shoe. I helped that friend to get it out. Then I saw suddenly a guy smiling, I think my age.. so I smiled back and then his smile got bigger and he kept staring. Not even stared at my friend. My friend kept looking and said he didn't even notice me looking weird at him bc he kept staring and smiling at me.

I just don't get that kind of attention from men. I thought I should be nice bc he smiled, that's all.

Was he tryna say something with that kind of smile? His smile was like; smiling from ear to ear and he kept smiling like that and kept staring while he did that.
Or was he making fun of me? I'm not used to that kind of attention haha..
What was that kind of signal? Was he just being nice?
Post Opinion