The 'X Factor' host originally recorded the song but after he struggled to hit the high notes, he passed it on to the 'Talk Dirty' hitmaker and is now regretting not trying to make the pop track work for his voice.
A source told The Sun newspaper: ''Olly was a bit gutted to see it go on and become the song of the summer. But he has no hard feelings.
''He still likes listening to it. Although he has admittedly had a few doubts about whether he should have tried harder to make it work for him rather than letting another artist have it.''
The single has been one of the biggest-selling songs of the summer and has been top of the charts around the world, including reaching number one in the UK and going multi-platinum in the US.
Meanwhile, the 31-year-old pop star recently split up from his girlfriend property manager Francesca Thomas, 26, and reportedly had concerns about their relationship because he puts his music first.
A source previously said: ''The split has just happened and it is very raw for Olly, he still feels numb.
''He always worried that his relationship would struggle because he'd always put his career first.''
'The Now Now' will be released on June 29th, and two new teaser tracks have appeared - 'Humility' and 'Lake Zurich'.