[3] In the 2020–21 season, Nelson featured in a first-team squad during Leicester City's UEFA Europa League campaign.
[9] On 29 August 2023, he made his senior debut for Leicester as an 82nd-minute substitute for James Justin in a 2–0 away win over Tranmere Rovers in the Second Round of the EFL Cup.
[3] On 9 December 2023, he made his league debut in the EFL Championship for Leicester as an 81st-minute substitute for Jannik Vestergaard in a 4–0 win against Plymouth Argyle.
After making one appearance for Scotland's under-16 team,[14] he made his England U18 debut starting in a 3–2 defeat against the Netherlands on 11 November 2021.
[16] On 22 March 2024, Nelson made a goalscoring debut for the England Elite League squad during a 5-1 win over Poland at the Bialystok City Stadium.