The 16-year-old girl is featured in today's issue of The Sun, where it's reported that she and Nicholas, 17, were together for twelve months before he found fame on The X Factor and she cried after hearing his remarks about love on TV.
The girl told the newspaper that she and Nicholas dated before her family moved to Australia and kept in touch via phone while she was away. After two months her family moved back to Scotland and they gave their romance another go briefly before splitting.
However, Nicholas has now hit back via Twitter, saying: "So as we all know my ex,ex girlfriend went to the papers and told them we went out!! Ok no big deal it was 2 years ago get over it!! Love u all."
He later added: "I never lied about it I though it would be disrespectful to talk about it on national tv with 10 millions viewers !!! ... Any ways moving on I am in the final and staying focused and hopefully going to win. !! #TEAMNICKY."
Nicholas needs to stay focused as The X Factor final airs this weekend and he'll face competition from Sam Bailey and Luke Friend for the 2013 crown.
The Scottish singer will perform 'Angel' by Sarah McLachlan and 'Candy' by Robbie Williams before joining Westlife star Shane Filan for a duet of 'Flying Without Wings'.
The latter performance will be particularly special for Nicholas as Shane was one of the celebrities at his mentor Louis Walsh's judges' houses who pushed for him to reach the live shows.