This article may contain spoilers.
This dilemma can occur at any time in the game, but usually takes a few days to show itself. You do not have to have painkillers in your supplies stash for this dilemma to occur.
When faced with this dilemma, the player will be given information on the left with a bottle of pills in the center and options on the right. On the left side the player will be informed that one of your survivors has caught another survivor stealing painkillers. The thief will claim that they need the painkillers, but the other survivor doesn't trust them. From there you may choose who to side with.
On the far right side the following choices are displayed:
Take the pills.
Let it be.
Picking the first option will cause the thief to take some major stat penalties and they may lash out, breaking a limb or worse.
If you decide to let it be, the other survivor will not be happy and relationships will worsen.
In both instances relationships go bad and can result in fights and injury. Since you do not actually have to have painkillers for this to occur, there is no actual loss on supplies if you decide to let it be.