When I was a kid, someone called me a nerd for reading comic books and I stopped reading comic books, what mistake did I make?

Not being true to yourself,  if you enjoy reading comics do so.

You listened to others and allowed them to dictate your actions. I wasn't allowed to read comic books. According to my mother only stupid people enjoyed them.

When I was a kid everyone read comic books, the nerds were the ones that came to school dressed as comic book characters

It depends on what you did instead. If you used that time to apply yourself to your schoolwork, none.  If you started torturing small animals you should have stuck with the comic books.

You caved in to peer pressure, and gave up something you liked just because other people ridiculed you.  I was called a nerd for playing video games and liking computers in my day (idiotic to young folks today, I know)...so we all went through it in some way!