The pop star teamed up with country singer Kelsea Ballerini at the MGM Grand Garden Arena in Las Vegas ceremony to perform her song Peter Pan, but music fans were quick to note that Nick's guitar skills weren't quite up to par during one section of the track.

Detractors took to social media to criticise his set, which has since inspired a string of viral memes poking fun at his onstage mishap, and on Tuesday (05Apr16), Nick took to Twitter to laugh off the embarrassment.

"Just landed in London to all these videos from Sunday nights performance..So funny," he wrote. "Yes. I screwed up the solo thanks to a huge brain fart."

"We're all human.. And s**t happens sometimes," he continued, before expressing his amusement at one viral image of mocked-up sheet music from his set.

"But whoever made this... Truly genius," he added.

Nick's Tuesday Twitter posts were his first comments on the awards show screw up, after previously taking to the micro-blogging site on Monday (04Apr16) to send Kelsea a congratulatory note.

"@KelseaBallerini you killed it last night," he tweeted. "Congrats on a big night".

The duet was also a dream come true for Kelsea as she had long harboured a crush on the former Jonas Brothers star.

"I thought I was going to marry (Nick) when I was 13-years-old," she laughed to newspaper The Tennessean before the big show. "So, it's very casual that I'm on stage with him."

Kelsea's appearance at the 51st annual ACM Awards was made all the more special as she collected the New Female Vocalist of the Year prize, one of two honours she had been nominated for.