The defender was an integral part of the RtD U18 team, helping them win back-to-back Gothia Cup tournaments in 2014 and in 2015.
[3] On 2 August 2016, it was confirmed, that Mumin had signed a professional contract with Danish Superliga side FC Nordsjælland, and joined their U19 squad.
Mumin started on the bench, but replaced Viktor Tranberg in the 62nd minute in a 2–1 defeat against AaB in the Danish Superliga.
[7][8] Mumin got shirt number 6 and made his official debut for the club in the Primeira Liga on 18 September 2020 against Belenenses SAD, playing all 90 minutes.
[12][13] Mumin made his debut on 6 June 2024 in a World Cup qualifier against Mali at the Stade du 26 Mars.