The Scottish hopeful missed out on being crowned winner of this year's X Factor after 36-year-old prison officer Sam Bailey took home the title.
And although he is happy for fellow star Sam - who is on track to top the charts this Christmas - Nicholas has now admitted that he feels Gary and mentor Louis didn't show him enough support over the weekend.
Take That singer Gary was the only X Factor judge to not give Nicholas a standing ovation following his final performance on Sunday, leading the youngster to believe that Gary has always disliked him.
He told the Mail Online: "Gary had a problem with me throughout the whole show. He never seemed to like me and whenever I gave a good performance he would pick up on the smallest things in the world."
The teenager's mother was also hurt by Gary's refusal to stand after her son had taken to the stage for the last time and dubbed his decision to remain sitting as "unprofessional".
Meanwhile, Louis surprised viewers on Sunday evening (15 December) by encouraging everyone to vote for Sam instead of drumming up more support for his own contestant.
Nicholas added: "I was disappointed with Louis saying, "Vote for Sam and her single everyone." It felt like Sam was getting all the love."
The 17-year-old was also apparently one of the few acts who didn't celebrate his time on the show with the judges at Gary's after-show party later that night.
Nevertheless, he still appears to be in good spirits despite feeling let down.
Yesterday (16 December), Nicholas tweeted: "I just want to make a promise with all you guys and that is that I will never give up on your and hopefully I will have an album out soon."
He added this morning: "Can't wait to head home today and see everyone !! Going to have the best Christmas ever."
Neither Louis nor Gary have responded to Nicholas yet.
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