pustule vs bleb

pustule and bleb both are nouns.

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

As nouns, bleb is a hypernym of pustule; that is, bleb is a word with a broader meaning than pustule:

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

Other hypernyms of pustule include blister, bulla, hickey, pimple, zit.

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