Nicholls made his television debut in 1990 at the age of 10, in ''
Children's Ward''. In 1994, he appeared in the
BBC children's drama
Earthfasts and
The Biz, a teenage performing arts drama filmed at
Hampton Court. In 1996, he appeared in an episode of
Out of the Blue. Later that year, Nicholls began portraying the role of
Joe Wicks in the
BBC soap opera
EastEnders, a role which he played until 1997, and a cameo appearance in 2024. Nicholls appeared in several teenage stage roles, notably as
Aladdin in
Aladdin - Genie of the Ring at the Central Theatre in
Chatham (1996–1997), and he made his London stage debut as Billy Fisher in the 1998 production of
Billy Liar, at the
King's Head Theatre in
Islington. Nicholls' 2008 career began as the character Robert Fielding in
Harley Street alongside
Suranne Jones. He also played Harry Keegan in
Secret Diary of a Call Girl,
Judas in another BBC series entitled
The Passion, and appeared in
A Thing Called Love. He then appeared in the 2012 feature film
Life Just Is. Nicholls also appeared as Simon Marshall in the BBC hospital drama serial
Holby City between May and July 2012, and played Cal Beckett in Channel 4's crime thriller,
The Fear. He played the role of DS Sam Casey in
ITV's
Law & Order: UK until the end of series 7 in 2013. From 2017 to 2018, Nicholls portrayed the role of
Steve Bell in the Channel 4 drama
Ackley Bridge. From September to October 2018, Nicholls starred alongside Iwan Rheon in
Foxfinder at the
Ambassadors Theatre. In January 2019, Nicholls took over the role of Raymond from
Mathew Horne in the British touring production of
Rain Man. ==Personal life==