hickey vs pustule

hickey and pustule both are nouns.

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

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

hickey: 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 hickey include papule.

hickey (noun)	pustule (noun)
a temporary red mark on a person's skin resulting from kissing or sucking by their lover	a small inflamed elevation of skin containing pus; a blister filled with pus
a small inflamed elevation of the skin; a pustule or papule; common symptom in acne