The talent show judge was asked about throwing water over the music mogul, much like former judge Sharon Osbourne had done to his predecessor Louis Walsh, to which he replied: “That is always a classic... or acid.”
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Nick Grimshaw
The comments will not have sat well with Simon, who is an ambassador for Katie Piper’s charity.
The TV presenter suffered horrific burns when an ex-boyfriend threw sulphuric acid in her face in 2008.
Simon is now close friends with the star, who set up the Katie Piper Foundation to help people living with burns and scars.
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Simon Cowell with friend Katie Piper
After making the comments in a TV interview, Nick has now expressed his regret for the jibe.
Earlier this week, the Radio 1 Breakfast Show DJ admitted he “understands” why people “hate him”.
He faced a backlash from fans of the show when he replaced Louis on the panel earlier this week.
Of the controversy, he told Alan Carr on ‘Chatty Man’: “I knew I’d get the scrutiny as Louis Walsh is so loved.
“You’ve got to ignore it. My dad hates the Rolling Stones, so why can’t millions hate me?”
Nick is mentoring the Boys on the ITV talent show, having picked Mason Noise, Che Chesterman and Seann Miley Moore for the live shows.
‘The X Factor’ continues tonight (31 October) at 8pm on ITV.
'X Factor': Most Controversial Moments
Emily Nakanda's Happy-Slapping Scandal(01 of06)
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Back in series four, 15-year-old Emily Nakanda was one of the early favourites to win the show, but had to back out, after a video emerged showing her violently attacking another teenage girl.Reports at the time said Emily was asked to leave the competition by producers, or risk being axed. (credit:Ken McKay/Rex)
Frankie Cocozza Oversteps The Mark(02 of06)
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Frankie's hard partying during his time on 'X Factor' in 2011 was well-documented, but it ended up costing him his place in the competition, when he broke one of producers' "golden rules", later reported to have been the use of class-A drugs. (credit:Beretta/Sims/REX)
Grimmy And Rita Join The Show(03 of06)
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The addition of Nick Grimshaw and Rita Ora was - at least initially - a controversial one, with some critics wondering whether either of them had the relevant experience to find the UK's hottest talent. (credit:ITV)
The Six Chair Challenge(04 of06)
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The 'Six Chair Challenge' has been a sticking point with 'X Factor' viewers since its debut in 2013. Many have branded the final stage of Bootcamp cruel, with some hopefuls gaining a place at Judges' Houses only to have to give it up later, but Simon Cowell clearly doesn't mind, as it's back for 2015. (credit:Tom Dymond/Thames/Rex)
Louis Walsh Pushes Dannii To Breaking Point(05 of06)
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Louis repeatedly accused Dannii of stealing one of his acts' songs back in 2008, resulting in the 'Put The Needle On It' singer breaking down in tears live on air, and having to vacate the panel at one point to gather herself.Simon jumped to Dannii's defence, telling Louis: "Dannii made the right choice, Louis, if you don't like it, tough."You're always whining and complaining. You two have to kiss and make up." (credit:ITV)
Gamu-Gate(06 of06)
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A turning point for Cheryl's popularity with the British public came when she was met with a backlash for putting both Cher Lloyd and Katie Waissel through to the live shows, over viewers' favourite Gamu, despite neither of them finishing their performances at judges' houses.Reports later suggested that Gamu could be facing deportation from the UK - adding to the backlash against Cheryl - though the aspiring singer was later insistent this was not the case. (credit:Ken McKay/TalkbackThames/Rex)