swelled head vs self-importance

swelled head and self-importance both are nouns.

Word	Noun	Adjective	Verb	Adverb
swelled head	Yes	No	No	No
self-importance	Yes	No	No	No

As nouns, swelled head and self-importance are synonyms defined as:

swelled head and self-importance: an exaggerated opinion of your own importance

Other synonyms of swelled head include egotism.

swelled head (noun)	self-importance (noun)
an exaggerated opinion of your own importance	an exaggerated opinion of your own importance
	an inflated feeling of pride in your superiority to others