The 17-year-old college student, who is half Spanish, won over the judges and the audience with his passionate performance of the Enrique Iglesias ballad Hero at the first round of arena auditions.
The student said: "I'm trying to stay grounded as much as I can. Obviously my head will explode a little bit, but I think that's kind of understandable, being on national TV. But after a couple of days I'll be okay.
"My friends are the kind of people who will just give me a slap if they think I'm getting too big headed, so I think they will keep me grounded."
At his first audition Fernandez-Holt told judge Nicole Scherzinger he thought she was "hot".
He confessed: "I was just as surprised that it came out as everyone else was. It didn't really process in my mind that I was saying that to Nicole Scherzinger, on TV. And afterwards I just though 'Oh God!' So I'm just glad that she took it well.
"But she tweeted me last night and it's crazy."
Meanwhile, prison officer and mother-of-two Sam Bailey - who got a standing ovation from all four judges with her audition - revealed she has been overwhelmed by all the support she has received.
Sam said: "When I am on stage and I am singing I get to be someone else.
"I've been a prison officer for the last three years.
"And going from that to doing this has been absolutely amazing.
"I was worried, with my job, but the prison service have been absolutely amazing. The support from the prison and all the people in it has been amazing."