The 20-year-old boyband star had to take a hiatus from the group in April to recover from specialist surgery to fix a haemorrhaging nodule, but he surprised fans when he stepped back on stage last week at Capital FM's Summertime Ball.
Nathan, who sipped on honey and lemon as he spoke to Aled Jones and Lorraine Kelly on ITV's Daybreak earlier today, said: "It was pretty severe, I was pretty scared for a while. It wasn't pleasant."
"It's a lot better, there's still a bit of recovery to do, but slowly and steadily and all that," he added.
The boys - Nathan, Max George, Tom Parker, Jay McGuiness, and Siva Kaneswaran - spent some time in the States earlier this year filming their first fly-on-the-wall reality show called The Wanted Life, which premiered in the US at the beginning of this month.
The Wanted, who also performed their new single 'Walks Like Rihanna' on Daybreak, promised fans that they wouldn't be relocating to the States any time soon.
While Max described the LA lifestyle as "very laid back", the boys unanimously declared that they would "always" choose the UK.
The Wanted Life premieres on E! in the UK on 24 June.
Watch the music video for 'Walks Like Rihanna' below: