Maybe the story involves some secrets that are not meant to be shared. It could also be that there are some parts of the story that are too personal or embarrassing for Nick.
First, you could try to talk to Nick and see if he is willing to let you tell the story. If he isn't, then just let it go. You might also consider writing the story down for yourself as a way of processing the clue, but without sharing it with others.
This could be due to a bug. Try reloading an earlier save and see if the issue persists. Sometimes glitches happen during gameplay that can disrupt quest progression.
Maybe it's a bug in the game. Try restarting the game or the relevant level. Sometimes glitches can be fixed simply by refreshing the system.
One reason could be his own clumsiness. Maybe Peter is always in a rush and not paying enough attention to his surroundings. For example, he could be running down the stairs while looking at his phone and trip, resulting in an injury.
Maybe he was involved in some rough sports. For example, in a game like rugby where there is a lot of physical contact, a wrong move could lead to such an accident.
One possible reason could be that he was framed for a serious offense he didn't commit. Maybe someone planted false evidence of him attacking a fellow student. Another reason might be that he continuously defied the school's strict rules in order to pursue his own goals of getting stronger faster, which the school authorities couldn't tolerate.
It could be a word like 'plot' or 'tale'. Those are common terms associated with narratives and stories in crosswords.
One reason could be that he was exposed to some kind of harmful chakra or energy in the village. Maybe some leftover dark jutsu residue affected his weak baby body.
In fanfiction, one possible reason could be that he was exposed to some kind of harmful chakra. Maybe an enemy sent a weak but insidious chakra wave towards him when he was just an infant, which gradually made him sick. Another reason might be related to the poor living conditions he was in. Since he was alone as an infant without proper care, he could have caught a disease easily from the dirty environment around him.
It could be due to an accident, like a gas leak or faulty machinery.