He felt the line carefully with his right hand and noticed that it was
bleeding.” "The sun, and the constant movement of his fingers, had
by this time completely recovered his cramped left hand." So the
right hand was sling out of blood, left hand due to the use of too long
cramp.
His right hand was numb when he caught the big fish for the first time,
and his left hand was not strong enough to soothe the big fish for the
second time, which caused his right hand to be injured.