Tony insists on treating Steve's injuries and is going to give him some kind of painkiller, but Steve explains that it won't work. Nothing will.
Tony asks if by 'nothing' he means nothing and asks what all they tried. Steve goes through a list.
So Tony asks what happens if he gets injured and Steve explains that he gets patched up, heals 4 times faster, and until he's fully healed remembers to 'Duck faster.'
Tony is properly horrified and starts making plans to improve Steve's armor.
I know it's not much and I'm really sorry about that. Anyone know which fic I'm talking about???
EDIT: This fic was found, thank you!
It Will Probably Accelerate by northatlantic