A.Daniel's statement downplays how serious his injury is in the hope that he can stay in the game.
This phrase it's just a scratch is used when one gets hurt and does not want a big fuss to be made over the injury. It's one of Mercutio's lines in Romeo and Juliet. He says it after Tybalt has stabbed him under the arm. Mercution says that his injury is just a scratch but he is lying since he next says that he is headed towards his grave.
