After emerging through Levski Sofia's youth system, he made his professional debut in the second level with Spartak Pleven, the club from his home town.

On 6 October 2004 Nikolov scored his first goal in a 6–0 drubbing of amateur side Botev Lukovit of Bulgarian Cup.

Plamen quickly became part of the main team and for two seasons earned 53 appearances, scoring two goals.

In 2007–08 A PFG season coach of Litex Miodrag Ješić decided to put Nikolov into the starting line-up as center back.

In February 2012 Nikolov signed for FC Tom Tomsk on loan until the end of the season, before joining the club permanently in the summer of the same year.