contusion vs hitting

contusion and hitting both are nouns.

Word	Noun	Adjective	Verb	Adverb
contusion	Yes	No	No	No
hitting	Yes	No	No	No

As nouns, hitting is a hypernym of contusion; that is, hitting is a word with a broader meaning than contusion:

Other hypernyms of contusion include hit, striking.

contusion (noun)	hitting (noun)
the action of bruising	the act of contacting one thing with another
an injury that doesn't break the skin but results in some discoloration