Should the narrator call them by their nickname right away?

[JustHANO]

Situation goes like this. Guy finds girl Id and states her name. I'll be writing her nickname for the rest of the story, but we don't know the nickname yet. Should I start by calling her by the ID name then transition when she states her nickname.

Also it's not a situation where she can just go "Dont call me by that name, call me blahblah." So that won't work.

 

[XianPiete]

Situation goes like this. Guy finds girl Id and states her name. I'll be writing her nickname for the rest of the story, but we don't know the nickname yet. Should I start by calling her by the ID name then transition when she states her nickname.

Also it's not a situation where she can just go "Dont call me by that name, call me blahblah." So that won't work.

Once you introduce the nickname to your readers it's normal to use it. If your character is introduced as the mysterious girl, and you suddenly call her Weezy, people will be confused I imagine.

 

[Sabruness]

If it's been revealed even once to the readers, it's fine to use it when referring to the character outside of character speech.

 

[Jemini]

If it's been revealed even once to the readers, it's fine to use it when referring to the character outside of character speech.

More or less this, but it also somewhat depends on the tone and perspective of your narrator. Is your narrator some inner manifestation of the MC's perspective (3rd or 1st person, MC's POV,) or are they an omnicient 3rd person narrator? There are circumstances where the omnicient 3rd person narrator should never call a character by a nick name in case you are trying to keep up a certain tone. But, then, I guess if you are asking this question then you are likely not using that tone in the first place.

So, really, that entire paragraph I just wrote was not directed at the OP, but rather at whoever else may be reading this in order to know where the exceptions to the rule lie.