This is probably gonna sound boring, but if someone said to me, "Dude, you're staring." I'd just give myself a mental shake and say, "Oh. Uhhh, sorry. Just... lost in my thoughts."
At thirteen years old, I used to visit a roadside store that sold ice cream. More than once, the kid scooping ice cream behind the counter would wave his hand to get my attention, because I was just... staring at how pretty he was.
I didn't know it at the time, but that kid later grew up to be my husband. We only met that one summer, then reunited by chance, in 2016.