He was born in Vinnytsia, Ukraine,[1] and gained worldwide attention when he won Group B of the 2007 Moscow Open at the age of 10.

In April 2008, Nyzhnyk won the Nabokov Memorial in Kyiv, Ukraine, with 8½/11, and scored his first GM norm.

[6] In January 2011, Nyzhnyk played in the Grandmaster Group C of the prestigious Tata Steel Chess Tournament in Wijk aan Zee, finishing in second place with 8½/13.

[7][8] In 2011, he tied for 1st-6th with Ivan Sokolov, Vladimir Baklan, Kamil Miton, Jon Ludvig Hammer and Yuriy Kuzubov in the MP Reykjavík Open.

[9] In August 2019, Nyzhnyk won the U.S. Open Championship in Orlando, Florida, scoring 8/9 to finish in clear first.