Well, there kinda isnt a difference, but there kinda is.
The difference is that a nerd is really smart but you dont have to be smart to be a geek. A geek is just really weird and socially awkward and they're obsessed with weird video games and comics and they know alot about computers and games.
A nerd is someones who's really smart or smarter than average academically. They dont always fit in in school and stuff because other kids wish they were as smart as us, LOL. Im kinda a nerd. I was really nerdy last year.
But yeah, there's kinda a difference but not really because they're used interchangeably. (whoa, big words!