It is a subtle indicator. It could mean that he agrees with you. You’re silly. Or that he has a deeper affection for you. It usually means he thinks your pretty and felt a moment of deep fondness and is trying to let you know there is something there.
I never wink unless it is to a child that I am letting know something like “I understand” or “It’s ok” when their parents yell at them or they look embarrassed. OR to a cute or attractive woman I am saying something subtle about, like, “you’re gorgeous” or “I could totally adore you”.
There are several things it could be. I’d have to see it done to guess which it was.