I think my friend isn't interesting
Why don't you find them interesting?
He sounds like he speaks through his nose.
It's rude to assume your friend isn't interesting. Maybe you should move the conversation towards something you're interested in.
I should just go and talk about things that interest me? I don't think so, who's the adult here, that seems immature to me
You can express your interests without being selfish.   It is even possible that you may both find a mutual interest to talk about.