If I get an Egg, then the Shiny Charm, will the egg's shiny odds be boosted?

Question

Or do I need to 'produce' the Egg after recieving the Shiny Charm?

Comments

The egg is generated when you obtain it. once you have the egg, the details of the Pokemon inside can’t change

Answer 1

Is shininess determined by the personality number in every main series game from gen 3 onwards? If yes, when does the game generate a personality number for eggs in gen 9?

When the egg is generated.

source
Shiny charms work by changing the way the game generates personality numbers, so if the egg already has a personality, the shiny charm won't affect it.
source