full of oneself
Conceited, self-centered, as in Ever since she won the prize Mary's been so full of herself that no one wants to talk to her. This expression uses full of in the sense of “engrossed with” or “absorbed with,” a usage dating from about 1600.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.