How bad is it if I lie about my age to someone when I first meet them?

I’m a 27 year old female, but I look really young and can get away with saying I’m 22. I just met a guy and by reflex I said I was 22. He’s 23, but I think I really like him. Maybe. My thing is…. I don’t like the idea of leading him to think I’m younger than I really am; on the other hand I’m really sensitive about my age.

What might his reaction be when he finds out? [The preferred way for him to find out would be me confessing.]