"Stop being stubborn and let me help you!" Leon snaps as you try to push him away once more. "You're such a pain in the ass."

He's trying to help by wrapping up your wound. You, in typical fashion, don't want to accept the help.

Leon's really trying to convince himself that it's only because a wound of this severity going untreated would risk your entire mission. Not because he would be torn up if you died. And not because it would eat at him forever because he secretly cares. A lot.