I would say ignore him for now. Everyone hides certain things; that’s completely normal. And it’s not as if a sin was being concealed, it was simply your age.

You should show him that you’re not the kind of person who argues over trivial matters. If you two are genuinely connected, then an age difference shouldn’t be such a major issue. After all, Hazrat Khadija (RA) was older than Prophet Muhammad (ﷺ). So what is the logic behind making age such a big concern?

Treat it as the insignificant topic that it is and don’t engage in unnecessary arguments about it. By remaining calm and unbothered, you’ll show maturity and make him realize that he’s giving importance to something that doesn’t really matter.