The 'Hello My Love' hitmaker recalled how he was at a shop launch in London's Bond Street during Oasis' heyday in the mid-90s, and he and his bandmates were hyped to be in the same room as so many ''superstars'', including the 'Some Might Say' group, who split up in 2009.
The 'Flying Without Wings' singer, 40, thought he'd go up and meet his idol, Liam, the band's former frontman, but introducing Westlife - who had just formed in Dublin that same year - as their manager Louis Walsh's ''band'' didn't impress the notoriously outspoken 46-year-old rocker.
Recalling the snub from the 'Wall of Glass' hitmaker on Friday night's (11.01.19) episode of 'The Graham Norton' show, Nicky spilled: ''We were a young band in 1998, we'd just signed a record deal over here and we went to the opening of a big store in Bond Street and there were all these superstars including Oasis, who were so big.
''We thought, 'We have to go over and say hello,' so I tapped Liam on the shoulder and said, 'We're Louis Walsh's new band' and he just said F off!''
Nicky - who is joined by Shane Filan, Kian Egan and Markus Feehily in the group - also revealed that his kids aren't impressed that their dad is going to be back signing Westlife's ''rubbish songs'' on their forthcoming tour after they recently made their comeback with new single 'Hello My Love', which they perform on the show, from their first album in almost eight years.
The 'You Raise Me Up' star - who has twin sons Rocco an Jay, 11, and five-year-old daughter Gia with wife Yvonne - admitted: ''They are at that stage when they say, 'Dad, you're not going to sing all those rubbish songs from the past are you?'''
'The Graham Norton Show' airs on BBC One from 10.35pm.
How are the world's biggest superstars changing?
Graham J tells all about his experience with the Jazz Journal.
An interview with Nick Wilson.
He dropped his newest single Losing Sleep earlier this year.
Seven ways you can be greener at a music festival.
Listen to their song 'She Takes You Under' now.