I got a penis question

Bella • #JBGANG Mommy of kailani Rose!

Okay I'm about to sound dumb as fuck but, my boyfriend is uncircumcised and is a good size for me sex wise. However he said the other day that it's supposed to get a little bit bigger as in it's gonna grow some more. I went with it because what could I say? 🤷🏼‍♀️ I always thought that at 18 everything kinda stopped growing including a dick so if it's 3 inches at 18 like sorry dude you're done. But he's dead serious when he says it's gonna grow a little more. Is this true?