Pett began his senior career at hometown club Potters Bar Town after progressing through the youth ranks to establish himself in the first team during the 2009–10 season.

[15] He made his debut on the opening day of the 2014–15 season, playing 88 minutes in the club's 1–0 home victory against Hartlepool United on 9 August 2014.

[16] Pett scored his first goal for the club on 6 September 2014, briefly restoring parity in an eventual 3–2 defeat to York City.

[19] Pett scored with a "blistering strike" in a 1–0 home victory over Portsmouth on 14 April 2015, strengthening the club's place in the League Two play-off spots.

[20] The club went on to play Southend United in the play-off semi-finals, with Pett scoring in the second leg; Stevenage ultimately lost 4–2 on aggregate over the two games.

[23] During the 2015–16 campaign, he was a first-team regular playing in a deeper midfield role under new manager Teddy Sheringham as Stevenage finished that season in 18th-place in League Two.

[39] Pett went on to score seven times in 34 appearances during the first half of the campaign,[36] including his first brace for Stevenage in a 4–1 win against Cheltenham Town on 1 January 2018.

[42] Stevenage received a "significant five-figure" offer for Pett from fellow League Two club Lincoln City towards the end of the month,[42] which was accepted.

[44] Pett scored his first goal for Lincoln in the club's 1–1 home draw with Yeovil Town on the final day of the regular season.

[45] Pett's goal, a 20 yards (18 m) equaliser late in the second half, helped Lincoln earn the point they needed to secure their place in the League Two play-offs.

[51] By the time he regained his fitness, manager Danny Cowley, who had brought Pett to the club, had departed and was replaced by Michael Appleton, who told him that he would not play in any further League One matches but would continue to train with the first-team.

[54] Pett made his first appearance since returning to Stevenage in the club's FA Cup first round match with Concord Rangers on 7 November 2020, assisting the first goal in an eventual penalty shoot-out victory.

[65][66] He started in the play-off final at Wembley Stadium as Vale secured promotion with a 3–0 victory over Mansfield Town; Michael Baggaley of The Sentinel wrote that "[Pett was] calm, composed and classy in the midfield to help his side control the game".

[67][68] Pett underwent an operation to fix a niggling spinal disc herniation in his back in the 2022–23 pre-season and had to regain his fitness during the early part of the campaign, whilst new signing Funso Ojo was in good form in midfield along with Conlon, Walker and Garrity.

[74][75] He quickly established himself in a deep-lying midfield role, surrounded by Liam Sercombe and one of Curtis Thompson and Elliot Bonds.

[80] Manager Micky Mellon described him as "the complete midfielder", which he needed following injuries to Tom Conlon and Corry Evans, as well as the departure of Sam Clucas.

[8] Speaking in March 2023, he described his strengths as reading the game, winning the ball and making passes to transition the team from defence to attack.

[82] Pett was a talented cricketer in his youth and spent time on the books at Hertfordshire and Middlesex before he decided to focus on football.