self vs someone

self and someone both are nouns.

Word	Noun	Adjective	Verb	Adverb
self	Yes	Yes	No	No
someone	Yes	No	No	No

As nouns, someone is a hypernym of self; that is, someone is a word with a broader meaning than self:

self: a person considered as a unique individual
someone: a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

Other hypernyms of self include individual, mortal, person, somebody, soul.

self (noun)	someone (noun)
your consciousness of your own identity	a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential
a person considered as a unique individual

self (adjective)	someone (adjective)
(used as a combining form) relating to--of or by or to or from or for--the self