ulcer vs lesion

ulcer and lesion both are nouns.

Word	Noun	Adjective	Verb	Adverb
ulcer	Yes	No	No	No
lesion	Yes	No	No	No

As nouns, lesion is a hypernym of ulcer; that is, lesion is a word with a broader meaning than ulcer:

ulcer: a circumscribed inflammatory and often suppurating lesion on the skin or an internal mucous surface resulting in necrosis of tissue
lesion: any localized abnormal structural change in a bodily part

ulcer (noun)	lesion (noun)
a circumscribed inflammatory and often suppurating lesion on the skin or an internal mucous surface resulting in necrosis of tissue	any localized abnormal structural change in a bodily part
	an injury to living tissue (especially an injury involving a cut or break in the skin)