Suck your own dick
Example:
DeeDee: Did you have fun at the bar last night with Danny?
NJ: Eh, I couldn't really get a word in because he just sucked his own dick the whole time.
DeeDee: What! I didn't know you could suck your own dick.
NJ: I just mean he wouldn't talk about anything except for how cool he is. I don't care how many famous people he hangs out with or how many parties he gets invited to, but that's all he cares about.
DeeDee: Did you have fun at the bar last night with Danny?
NJ: Eh, I couldn't really get a word in because he just sucked his own dick the whole time.
DeeDee: What! I didn't know you could suck your own dick.
NJ: I just mean he wouldn't talk about anything except for how cool he is. I don't care how many famous people he hangs out with or how many parties he gets invited to, but that's all he cares about.