How quickly should a reader understand a character's personality?

Hey guys, currently working on my first novel. I have a concern with a side character. To me, he reads as kind of boring and uninteresting until around the 5000 word mark. I know this is a super vague question, but is that okay? I don't really know how to go back and make his personality more prevalent sooner, and I'm not even sure it's something I need to worry about, but I thought I'd ask to see if anyone had struggled with anything similar.

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EDIT: to add some clarity, when I say side character, what I really mean is a character like Ron or Hermione from Harry Potter. Not the main character, but someone who is present for a good majority of the chapters and events.