He was of Grandmaster strength at his peak in the early 1960s, but never received an international chess title. He played in three Soviet finals (1966, 1967, 1971). He represented Ukraine in two team matches against Bulgaria, in 1962 at Kiev where he scored 2/2, and again in 1968 at Odessa where he scored 1/1.
An excellent performance in the 1967 Soviet Team Championship at Moscow saw him post 7/9.
He played in the Soviet final that year at Kharkov, which had a Swiss format and over 100 players. The winners were Mikhail Tal and Lev Polugaevsky.
Chessmetrics.com, a site which ranks historical chess performances, ranks Nikolaevsky as high as 38th in the world, with a rating of 2634, in early 1960. This is Grandmaster territory.
There is a selection of 105 of his games at ChessGames.com.