How best to handle revealing a main character's name midway through a long story in close-third person?
I'm writing a novel, and it's written in close third person perspective, very much sitting on the shoulder of one main character and privy to their thoughts. There is another very important character who goes only by his nickname for most of the novel, but who will mostly likely tell the main character his real name about a third of the way through the story.
My first instinct is to have the narrative switch from " Nickname said, 'why don't we do this?' " to " Realname said, 'why don't we do this?' " after the main character learns his name, but I worry that this will be hard for the reader to get used to after several hundred pages of Nickname and possibly even confusing. Nevertheless, once the main character knows the real name and has started to use it, it seems terribly awkward to keep referring to him by the nickname.
Is there any (relatively) canonical way of handling this / are there some good examples of either method?
Edit: Here is a set of 3 links to short articles on the close third perspective, just for reference on the difference between that and straight up 3rd person.