Sam sat down at the table. "It's just a graze, Dean."
Dean ignored him. He put the first aid kit onto the table and, after sorting through it, brought out a pair of scissors. Turning back to Sam, he cut open the blood-dappled sleeve of his shirt and laid bare the wound, which was merely a graze.
"Dean, I –" Sam tried again.
"Shut it."
Trying to keep calm, Dean cleaned his brother's "wound" and slapped a bandage on it.
Then, job finished, he looked Sam in the face and said through gritted teeth, "Next time I say duck, DUCK!"