Speaking to Channel Seven's Sunrise program on Friday, he said the best part of the day was defeating his arch-nemesis Ultron on the steps of the Sydney Opera House.
"It was pretty amazing," Domenic told presented David Koch.
His mother, Nicole Pace, said her son was excited leading up to the big day.
"It brings so much excitement in the lead-up to it and then when it finally happens, it's just such a joyous occasion for not only him, to experience but our family as well and friends and everyone involved," she told Sunrise.
"It's just a day that he can look back to, if he does have a bit of a struggling day or a tough day, he can just remember back to this wonderful day that he had.
"It was a phenomenal amount of people involved, so many people behind the scenes and all of Sydney involved as well, family friends, his nurses and doctors.
"It's something we will treasure and remember forever."
Actor Robert Downey Jr, who plays the famous superhero on screen, congratulated Domenic via YouTube.
"Hey Domenic, it's Tony. I'm a little undercover right now. I've shaved the beard, hat and glasses, because in case you don't know there was a civil war recently," Downey Jr said in the video.
"Trying to keep it on the DL. Anyway, I've heard you've had quite the day. It's hard work saving the world isn't it?"
Battling cystic fibrosis, Domenic got to wear the suit on Thursday as part of an initiative from the Make A Wish Foundation.
He was put to work by NSW Police Commissioner Andrew Scipione who called Sydney’s own ‘Iron Boy’ to help keep residents safe.
“Iron Boy, we need your help,” the commissioner said.
“Make a Wish reporter Hope Joy has been kidnapped, officers have confirmed that Clark Island has been overtaken by Ultron’s henchmen and Hope Joy has been held captive.
“If I could make one wish, it would be for you to help us Iron Boy.”
The youngster was picked up by police helicopter while playing in a local park in Bringelly and taken to police headquarters for a briefing by the Commissioner.
He was told that Sydney was in trouble and the police needed help.
He was given a specially made suit in the same style as that of his favourite super hero, Iron Man, and battled Marvel nemesis Ultron at the Opera House as a crowd of supporters watched on.
Ms Pace told Make a Wish that Domenic was a very caring child.
“He always wants to know what’s going on around him in the world and how he could help others,” she said.
“I guess the final straw was when he stood up at the dinner table and said ‘I am Iron Boy’, then we pretty much had to go with it from then.”
Downey Jr endorsed the super hero quest on Thursday with a tweet.
The hashtag #IronBoyAU has gone viral on social media.
