Nikishyn won a bronze medal in the team men's épée event at the 2006 World Fencing Championships in Turin, Italy, a silver medal in the team men's épée event at the 2013 World Fencing Championships in Budapest, Hungary, a gold medal in the team men's épée event at the 2015 World Fencing Championships in Moscow, Russia, a bronze medal in the individual men's épée event at the 2018 World Fencing Championships in Wuxi, China, and a silver medal in the team men's épée event at the 2019 World Fencing Championships in Budapest, Hungary.