a tin god
(little) tin god
A pompous person. My attraction for him waned after he spent the entire evening acting like a little tin god. Everyone on the school board acts like a tin god. It's so irritating!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
a tin godor
a little tin godmainly BRITISH, LITERARY
If someone behaves like a tin god or like a little tin god, they behave as if they are much more important and powerful than they really are. So what are his qualifications for acting like a little tin god?
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012