What does Curley do to Lennie?

Curley attacked Lennie and started a fight.

Curley was balanced and poised. He slashed at Lennie with his left, and then smashed down his nose with a right. Lennie gave a cry of terror. Blood welled from his nose.

"George," he cried. "Make 'um let me alone, George."

He backed until he was against the wall, and Curley followed, slugging him in the face. Lennie's hands remained at his sides; he was too frightened to defend himself.