Nathan was in the band with Max George, Siva Kaneswaran, Jay McGuiness and Tom Parker, but the group decided to take a hiatus in January 2014 to pursue personal endeavours.
Now going forward as a solo artist, Nathan said on ITV's Lorraine: "I miss the constant banter. There was always something happening and someone was always playing a prank, so you were always on your toes, but now you're on your toes in a different way."
Nathan said he is still in contact with the boys too: "I had a lovely message from Jay the other day. He was like, 'I'm very tired today but your music's getting me through the day'."
Speaking about going solo, Nathan said: "It's obviously very different but I'm really enjoying it. It's been such a great experience writing the album and finding this sound that I've taken into my own.
"When we decided that we were going to take a break, I was only 20 years old. I can't stop doing what I love."
Nathan, whose new single 'Kiss Me Quick' is out on Sunday, added: "The fans have been incredible. I got to go on a UK tour and it sold out without them really hearing the track. They've been amazing."
Nathan's debut album is due out later this year.
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