I (18m) lied to my friend (32m) about my age online. How can I admit this to him?

Firstly, I’m 18.

However, a few months ago I befriended someone online a week before my 18th birthday. This was on Reddit (on a friend finding sub), and then eventually we chatted on discord. Despite being a week from turning 18, I told him I was 18.

It might not seem a big deal but in that week preceding my birthday we had intimate conversations. We sexted, basically. In my country (England) this would still be legal so he can’t get into trouble. But morally and ethically, I know he would be averse to this if he knew. He is very well read and interested in morality, meaning this situation is leagues worse than some others I see.

I feel I need to tell him. I want to meet him in real life and build a real friendship with him, but this is haunting me. It was dumb and I already know that. I just want a way of coming clean.