swelling vs bunion

swelling and bunion both are nouns.

Word	Noun	Adjective	Verb	Adverb
swelling	Yes	No	No	No
bunion	Yes	No	No	No

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

swelling (noun)	bunion (noun)
the increase in volume of certain substances when they are heated (often accompanied by release of water)	a painful swelling of the bursa of the first joint of the big toe
something that bulges out or is protuberant or projects from its surroundings
an abnormal protuberance or localized enlargement