Núñez scored his first professional goal for Metro Gallery on 6 March 2016, in a 2–3 away loss to Wong Tai Sin.

On 11 July 2022, Núñez was named to the preliminary squad in preparation for the 2022 EAFF E-1 Football Championship.

On 19 July 2022, Núñez made his international debut for Hong Kong in a 2022 EAFF E-1 Football Championship match against Japan.

On 26 December 2023, Núñez was named in Hong Kong's squad for the 2023 AFC Asian Cup.

[7] The fifth of six children, Núñez was born in Hong Kong to a British father and a Mexican mother.