male genitals vs genital organ

male genitals and genital organ both are nouns.

Word	Noun	Adjective	Verb	Adverb
male genitals	Yes	No	No	No
genital organ	Yes	No	No	No

As nouns, genital organ is a hypernym of male genitals; that is, genital organ is a word with a broader meaning than male genitals:

Other hypernyms of male genitals include crotch, genitalia, genitals, private parts, privates.

male genitals (noun)	genital organ (noun)
external male sex organs	external sex organ