[2] At the junior level, Nin Reyes won the bronze medal on the vault at the 2012 Pan American Championships.

[9] He then tied with Sean Melton for the silver medal on the horizontal bar at the 2014 Pan American Sports Festival.

[10] Then at the 2014 Central American and Caribbean Games, he won the silver medal on the vault behind Cuba's Manrique Larduet.

[12][13] Nin Reyes won the bronze medal on the horizontal bar at the 2015 Sao Paulo World Cup.

[17] Despite fracturing two of his fingers,[18] he still competed at the World Championships in Glasgow, but he did not advance beyond the qualification round, finishing 96th in the all-around.

[6] He represented the Dominican Republic at the 2017 Summer Universiade held in Taipei, Taiwan, and he won the gold medal on the vault.

[18] At the 2018 Osijek World Challenge Cup, Nin Reyes won the bronze medal on the parallel bars,[26] and he placed fifth on the vault.

[27] Then at the Koper World Challenge Cup, he won the silver medal on the horizontal bar,[28] and he placed sixth on the vault.

[41] At the 2020 Melbourne World Cup, he finished eighth in the vault final,[42] earning 12 Olympic qualification points.

[41] Nin Reyes competed at the 2021 Pan American Championships in Rio de Janeiro, his final opportunity to win an Olympic spot.

[46] At the end of 2022, he injured a ligament in his right ankle, but he chose to not undergo surgery in order to compete for the spot at the 2024 Olympic Games.

[48] Then at the 2023 Central American and Caribbean Games, he won the silver medal in the all-around behind Cuba's Diorges Escobar.

[49] Then in the event finals, he won gold on the vault,[50] silver on the horizontal bar,[51] and bronze on the pommel horse.

[59] As of 2023, Nin Reyes is a student at the Universidad Autónoma de Santo Domingo where he studies physical education.