zit vs pustule

zit and pustule both are nouns.

Word	Noun	Adjective	Verb	Adverb
zit	Yes	No	No	No
pustule	Yes	No	No	No

As nouns, pustule is a hyponym of zit; that is, pustule is a word with a more specific, narrower meaning than zit:

zit: a small inflamed elevation of the skin; a pustule or papule; common symptom in acne
pustule: a small inflamed elevation of skin containing pus; a blister filled with pus

Other hyponyms of zit include papule.

zit (noun)	pustule (noun)
a small inflamed elevation of the skin; a pustule or papule; common symptom in acne	a small inflamed elevation of skin containing pus; a blister filled with pus