In 1903 he relocated as a professor to the Kharkiv University. In 1919 he was elected a member at the Academy of Sciences of the Ukraine. Among his written works were Herpetologia Caucasica (1913), and volumes on reptiles and amphibians that were part of the series "Fauna of Russia and Adjacent Countries".
He is the taxonomic authority of several reptile species. The viper species Vipera nikolskii (Nikolsky's adder) is named in his honor. Today in Russia, the "Nikolsky Herpetological Society" commemorates his name.