"Look there," said Hagrid, "see that stuff shinin' on the ground? Silvery stuff? That's unicorn blood. There's a unicorn in there bin hurt badly by summat. This is the second time in a week. I found one dead last Wednesday. We're gonna try an' find the poor thing. We might have ter put it out of its misery."
(Harry Potter and the Sorcerer's Stone)
What is the formal expression for ‘bin hurt’?