sovereign vs self-governing

sovereign is a noun but self-governing is not a noun.

Word	Noun	Adjective	Verb	Adverb
sovereign	Yes	Yes	No	No
self-governing	No	Yes	No	No

As adjectives, sovereign and self-governing are synonyms defined as:

sovereign and self-governing: (of political bodies) not controlled by outside forces

Other synonyms of sovereign include autonomous, independent.

sovereign (noun)	self-governing (noun)
a nation's ruler or head of state usually by hereditary right

sovereign (adjective)	self-governing (adjective)
greatest in status or authority or power	(of political bodies) not controlled by outside forces
(of political bodies) not controlled by outside forces