bleb vs pustule

bleb and pustule both are nouns.

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

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

bleb: (pathology) an elevation of the skin filled with serous fluid
pustule: a small inflamed elevation of skin containing pus; a blister filled with pus

Other hyponyms of bleb include water blister, blood blister.

bleb (noun)	pustule (noun)
(pathology) an elevation of the skin filled with serous fluid	a small inflamed elevation of skin containing pus; a blister filled with pus