self-governing vs sovereign

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

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

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

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

Other synonyms of self-governing include autonomous, independent.

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

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