burnt: damaged or injured by burning
Your hand looks badly burnt.
"Burn" often connects to "fire"
I am not sur if we say "to get burnt by the boiling water"?
You can definitely use burn to describe injuries from boiling water, but the more specific verb is scald, which refers to injuries from boiling liquid or steam.
He was scalded by the boiling water when he dropped the pot. He got several second degree burns.
A thesaurus is often useful when you want to find a word with a specific meaning, and you only know a word with a related or more general meaning.
In this case https://www.thesaurus.com/browse/burnt gives some useful suggestions:
charred parched scalded scorched seared singed
You need to check each one. For example "charred" means "slightly burnt at the edge" and "seared" means "burnt only on the surface (eg a meat steak)" These are no good. But scalded means "to burn or affect painfully with hot liquid or steam." That is the exact meaning you want.
A thesaurus is the right tool to answer this kind of question.