The star and his Jonas Brothers bandmates Kevin Jonas and Joe Jonas wowed the crowd when they performed their track "What a Man Gotta Do" at the ceremony last month (January), but the singer was embarrassed when he discovered he had been making headlines for all the wrong reasons.
And Jonas admitted he's "annoyed" no one informed him of the dental snafu before the cameras caught it.
"Here's the thing that's really frustrating about this, OK? First of all, there was spinach in my teeth from my breakfast, which I ate hours before. So the entire day, no one thought to be like, 'Hey man, there's something back there,' " he said on "The Tonight Show Starring Jimmy Fallon".
After the Jonas Brothers left the stage, their manager gave Nick the bad news, leading him to check his phone - where he found a message from Adam Levine.
"We were really excited because the performance went pretty well and it was like our Grammy moment. Our return," Nick added. "I was so amped and I was like, 'What'd you think?' and he's like, 'Well, just don't check (texts on phone)!' "
He immediately checked his phone only to discover a teasing text from the Maroon 5 frontman.
"The first message on my phone was from Adam Levine. He's like, 'Nice performance. You had a little schmutz in your teeth.' "