protuberance vs nubble

protuberance and nubble both are nouns.

Word	Noun	Adjective	Verb	Adverb
protuberance	Yes	No	No	No
nubble	Yes	No	No	No

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

protuberance: something that bulges out or is protuberant or projects from its surroundings
nubble: a small lump or protuberance

Other hyponyms of protuberance include frontal eminence, occipital protuberance, belly, caput, mogul, nub, snag, wart.

protuberance (noun)	nubble (noun)
something that bulges out or is protuberant or projects from its surroundings	a small lump or protuberance
the condition of being protuberant; the condition of bulging out