This is really bugging me, but I’m afraid there’s not much to go on.
In the scene, Character A puts (I think) Mercurochrome on Character B’s hands while B is sleeping with exhaustion, having just finished some difficult task that caused blisters. B’s hands stir a little, but B doesn’t wake. I want to say B is a child, but I’m not sure.
There’s also possibly a Character C in this scene that A is talking to, but again I can’t be sure.
This is very possibly a children’s or YA book, as it seems like an old memory to me. Could also be Stephen King, I read him a lot as a kid.
Sorry there’s not more. I’ll try to answer questions, but I’m pretty sure this is all I remember. Thanks in advance!