In 2014 Koroknai became the Hungarian national champion in the 400 metres hurdles.[3] He retained the title at the 2015 Hungarian Athletics Championships held in August 2015.[4]
in August 2020, he won the 400 metres hurdles title again at the Hungarian Athletics Championships in Budapest, winning in a time of 50.56 seconds.[5] In September 2020, he ran a new personal best time when he ran 49.71 seconds on the 5 September 2020 in Székesfehérvár. It came after he had not long returned to action after a prolonged absence from competing after being ruled out with a serious Achilles’ tendon injury.[6] It proved to be the nineteenth fastest time recorded worldwide during the year, in what was a curtailed season due to the coronavirus pandemic.[7]
He retained his Hungarian national 400 metres hurdles title at the 2021 Hungarian Athletics Championships, held in Debrecen in June 2021, running a time of 49.77 seconds.[8] He qualified for the delayed 2020 Summer Olympics in Tokyo, Japan, he competed in the 400 metre hurdles race. He ran a time of 49.80 seconds in the heats, but did not qualify for the semi-finals.[9]
