Aaron Lewis -- Sorry I F'ed Up The National Anthem

Staind frontman Aaron Lewis says it was a simple case of nerves that caused him to screw up the lyrics to the "Star-Spangled Banner" ... and now he wants the country to forgive him.

In case you missed it ... Lewis rearranged the lyrics pretty badly, screwing up almost immediately. But he quickly rebounded and didn't do a terrible job overall.

Still ... he's pretty embarrassed about the whole thing and took to his website to apologize for the blunder. He wrote, "All I can say is I'm sorry and ask for the Nation's forgiveness. My nerves got the best of me and I am completely torn up about what happened. America is the greatest country in the world."

He added, "I hope that the Nation, Major League Baseball and the many fans of our national pastime can forgive me."

What's particularly funny about the whole thing is that back in 2011, Lewis ripped Christina Aguilera for flubbing the anthem at the Super Bowl.

Karma is a real thing.