Born in Cardiff, Nicholls began his career at Leeds United, joining the Yorkshire club at the age of 12.
[3] He began training with the first team at the start of the 1989–90 season and roomed with Vinnie Jones for the first six months of his time with the squad.
The injury was originally misdiagnosed by the club's medical staff and he was put back into reserve team action after just three months and further damaged the ligament when attempting a tackle.
He was given an extension to his contract to prove his fitness but suffered a second serious injury soon after his return after tackling Gary McAllister in training that ruled him out for another six months.
[3] Nicholls spent two weeks on trial with Bristol City and was set to join the club until manager Russell Osman was sacked.