I always thought that "All Star" was by the Backstreet Boys until I was in college and I learned I was wrong.
Had you been wondering about this beforehand?
Yes.  I always told my friends that I doubted that "All Star" was by anyone but the BSB
It's okay to be unsure about who sings a song, and if you feel certain about it, it's okay to misattribute the song out of ignorance.  However, once you know the real answer, you should be ready to correct any misstatements you made in the past.  Your friends will respect you for it.
I don't care.
You need to own up to your mistakes and even laugh about it with your friends maybe. It's not a big deal to get an artist of a song wrong and a lot of people do it.