The Apprentice star will replace Jeff Stelling as host of the Channel 4 quiz show.
Hewer told TV Choice. "I was nervous, because I'm not a tutored presenter. I don't know how it all works. I was quite anxious about it, but they tell me I'm OK."
He continued: "The people who really know what they're doing are pleased, and in fact they're good enough to say it's going rather better than they thought it would. I'm enjoying it."
The former PR consultant also revealed that he had received permission from Lord Alan Sugar to pursue the Countdown hosting role.
"I said to him, 'What do you think?' [and] he said, 'Will it interfere with The Apprentice?'" explained Hewer. "I said, 'No, because I can exempt myself for the periods when it's filmed'. He said, 'Do it'. He was very good."
Former Apprentice candidate Kate Walsh recently backed Hewer's Countdown appointment, calling the decision "absolutely fantastic".
"He's such a nice person and the faces he pulls - he looks like he's sucking on a lemon a lot of the time - but I think he'll make it really fun and bring a lot of new viewers to the show," she said.
Countdown returns to Channel 4 on Monday, January 9 at 3.10pm.
> Apprentice star Nick Hewer on Countdown: First pictures