Self-important

It often happens that young shogi players become a little self-important, but I don't think that's something limited to the shogi world.

How self-important you are!

Don't be so self-important.

There are too many self-important people who do nothing important.

Tom's a terrible self-important person.

Near-synonym: self-entitled

The assistant manager was a self-important fellow who strutted about the office barking instructions.

But despite its plague of tunnels, the run-in on this route is of unusual interest to the locomotive enthusiast: besides the hordes of self-important saddle-tanks shunting in the extensive yards, there was at one time the chance of seeing those slender little North London engines, with their large outside cylinders and no visible storage place for coal, and also an occasional South Eastern locomotive sporting a lot of polished brass.