|Date of birth||2 October 1981|
|Place of birth||Hastings, England|
|Height||1.88 m (6 ft 2 in)|
|1998–2000||Queens Park Rangers|
|2000–2002||Queens Park Rangers||0||(0)|
|2002||→ Hayes (loan)||7||(0)|
|* Senior club appearances and goals counted for the domestic league only and correct as of 02:20, 1 October 2016 (UTC)
Bull was born in Hastings, East Sussex and moved to Aldershot Town in the summer of 2002 after being released by Queens Park Rangers. In his first season at the club he was named player of the year and scored his solitary goal for the club, a penalty in the final home match as promotion to the Football Conference was secured. He again won the Player of the Year trophy in the 2005–06 season.
In Aldershot's double-winning promotion season, Bull was named Goalkeeper of the Year and Non-League footballer of the Year by his peers. Despite his success, he said that he would leave Aldershot no matter what happened, and this was confirmed by the club at the end of the season. However, on 27 May 2008 it was announced that Bull would be staying on at Aldershot for a further two years. Bull played for Aldershot Town in their first game in the Football League against Accrington Stanley on 9 August 2008, which was won 1–0. He agreed to leave Aldershot at the end of July 2009 to pursue a career outside of football. However, he instead opted to continue his football career, and signed for Brentford on 3 August 2009. The following year, he turned down the offer of a further one-year contract with the Bees, and instead agreed a similar deal with Wycombe Wanderers on 7 June 2010. On 29 July 2010, Bull put in an outstanding performance against a Chelsea reserve side, making a very large number of saves and hampering Chelsea's efforts to score, which played a huge part in Wycombe's eventual 5–1 victory.
On 25 April 2011, Bull saved a penalty in a match against Crewe Alexandra at Adams Park. His save prevented Crewe from equalising and Wycombe went on to win 2–0. Bull played every first team game in both league and cup and was rewarded by winning both the supporters' and players' player of the year awards.
On 9 August 2011 Wycombe were involved in a penalty shootout against Colchester United in the first round of the League Cup. Wycombe won 5–4 on penalties after Bull saved a penalty in the shootout. On 8 November 2012 Bull left Wycombe by mutual consent.
Bull scored an injury time equaliser in the Kent derby at Tonbridge Angels on Boxing Day 2015. He also captained the side for the latter part of the season as Margate were promoted to the National League South via the play-offs after beating Hendon 1-0 and won the Players' Player of the Season award in 2014–15.
In December 2015, Bull was appointed manager of Margate until the end of the 2015-16 season. His appointment was subsequently extended until the end of the 2017-18 season. He resigned from his post in February 2017.
On 11 May 2018, Bull was appointed as first-team manager of Isthmian League Premier Division side Leatherhead on a two-year contract. Likewise with his spell at Margate, Bull will continue as a player/manager.
- Conference National (Champions): 2008
- League Two (Promotion): 2011
- "Keeper Bull will leave Aldershot". BBC Sport. 10 April 2007. Retrieved 16 July 2008.
- "Bull parts company with Aldershot". BBC Sport. 23 May 2008. Retrieved 16 July 2008.
- "Bull signs new deal after U-turn". BBC Sport. 27 May 2008. Retrieved 16 July 2008.
- "Accrington 0–1 Aldershot". BBC Sport. 9 August 2008. Retrieved 11 August 2008.
- "Shots to part company with Bull". BBC Sport. 20 July 2009. Retrieved 20 July 2009.
- "Bees snap up Shots star". Sky Sports. 3 August 2009. Retrieved 3 August 2009.
- "Blues hit Bull-seye". Wycombe Wanderers F.C. 7 June 2010. Archived from the original on 2012-03-14. Retrieved 7 June 2010.
- "Bull Scoops Blues awards". Buckinghamshire Advertiser. 9 May 2011. Retrieved 9 May 2011.
- "Nikki Bull leaves Wycombe". Vital Football. 10 August 2012. Retrieved 24 November 2012.
- "Margate sign keeper Nikki Bull". Isle of Thanet Gazette. 1 February 2014. Retrieved 23 May 2014.
- "Archived copy". Archived from the original on 14 July 2016. Retrieved 26 July 2016.
- "Archived copy". Archived from the original on 19 May 2016. Retrieved 26 July 2016.
- "Nikki Bull statement". Margate FC. 23 February 2017. Retrieved 26 February 2017.
- "Club News - New Manager Announcement!". Leatherhead Official Site. 11 May 2018. Retrieved 11 May 2018.
- Nikki Bull at Soccerbase