The Harry Potter star plays Neville Longbottom, who went from being a shy student to a hero in the final instalment of the franchise.
"It was a pretty daunting experience, to be honest with you. The film came out while I was flying to Australia," Lewis shared to The Telegraph. "When I landed there was all the news about [box office] records being broken, and various bits of press about me - all the headlines about how I'd been 'transformed'.
"I called [my publicist] Will and said, 'I don't like this'. It was very, very weird, and I suddenly felt very exposed. People started focusing on my appearance rather than my work, and I was uncomfortable with it.
"It was all very nice things they were saying, very flattering and humbling, but it was very odd. I just wanted to get back to [my hometown] Leeds and focus on work."
Lewis also confessed that he hated the false yellow teeth, fat suit and ear prosthetic he wore in the movies.
"When I was about 15 or 16, I hated it. I thought this is what the rest of the world thinks I am, what I really look like," he added. "I was so sick of the fat suit I used to take it off as soon as I came off set even if it was only for 20 minutes."
"Then I started to appreciate what it was all about. Becoming a character was important, and by the end I had a whole new appreciation of it. That fat suit and the make-up did help me get into the role. I'm glad I stuck with it."
Harry Potter and the Deathly Hallows: Part 2 was was released on DVD, Blu-ray, Triple Play and Digital Download last week.
Watch a 'Look Back' at the eight Harry Potter films below: