bleb vs blood blister

bleb and blood blister both are nouns.

Word	Noun	Adjective	Verb	Adverb
bleb	Yes	No	No	No
blood blister	Yes	No	No	No

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

bleb: (pathology) an elevation of the skin filled with serous fluid
blood blister: blister containing blood or bloody serum usually caused by an injury

Other hyponyms of bleb include water blister, pustule.

bleb (noun)	blood blister (noun)
(pathology) an elevation of the skin filled with serous fluid	blister containing blood or bloody serum usually caused by an injury