cheek vs body part

cheek and body part both are nouns.

Word	Noun	Adjective	Verb	Adverb
cheek	Yes	No	Yes	No
body part	Yes	No	No	No

As nouns, body part is a hypernym of cheek; that is, body part is a word with a broader meaning than cheek:

cheek: either of the two large fleshy masses of muscular tissue that form the human rump
body part: any part of an organism such as an organ or extremity

cheek (noun)	body part (noun)
impudent aggressiveness	any part of an organism such as an organ or extremity
either side of the face below the eyes
either of the two large fleshy masses of muscular tissue that form the human rump
an impudent statement

cheek (verb)	body part (verb)
speak impudently to