Born Erbach im Odenwald, Hessen, West Germany, Nikolov grew up in Sandbach in Hessen, starting playing football with local SG Sandbach. Nikolov started his senior career as backup, first to Uli Stein and then Andreas Köpke. After the latter left the team in June 1996 following the team's relegation from the Bundesliga he became first-choice, losing that status in early 2002 to newly-signed Dirk Heinen; he made his debut in the top division on 9 September 1995, playing the full 90 minutes in a 3–1 home win against 1. FC Kaiserslautern. In the following years Nikolov played in every season. In February 2007, after Pröll received a rib injury, he was reinstated by manager Friedhelm Funkel, contributing with 20 games during the team's 2006-07 season. In January 2010, it was announced that the 35-year-old Nikolov would not renew his contract with Eintracht that was due to expire in the summer, but he eventually signed a new deal until 2012, and later until 2013. In June 2013, Eintracht revealed that the goalkeeper's contract would be cancelled, effective immediately to allow Nikolov to fulfill his lifelong dream to play in the United States. On 19 June 2013, Nikolov signed with the Philadelphia Union of Major League Soccer. He made his first start as a Union player on 30 July 2013 in a friendly against Stoke City playing 45 minutes. Nikolov signed with Fort Lauderdale Strikers on 19 February 2014 on a contract for the nine-game Spring season. Nikolov started and played eight matches in goal for the Strikers, posting two clean sheets. The team ended up as runners-ups.
Nikolov also served as Assistant Coach for the Macedonian National Team.
Currently, Oka Nikolov serves as and Assistant Coach for the Philadelphia Union.
International career
Nikolov chose to represent the country of his ancestors, going on to win five caps for Macedonia in four years. He made his debut in a September 1998friendly match against Egypt but since he also possessed German citizenship he couldn't acquire a Macedonian passport and therefore was unable to play in official games under FIFA. His 5 appearances were only in friendlies. His final international was a match in November 2001 against Hungary.
