Nieves competed at the 2008 Spanish national championships, and finished first in the 10,000 meter T12 race. He competed at the 2008 Summer Paralympics in Beijing, China. After the 2008 Games, he changed coaches to Pablo Diaz and joined Gymnastic Society of Pontevedra athletic club. In 2009, he practiced in Pontevedra and Lugo, and he was coached by Pablo Diaz. In 2009, he had a goal of trying to go to the 2012 Summer Paralympics. At the 2009 IPC European Athletics Championships, he finished first in two races and finished second in another. He also set a world record in the 10,000 meters. His second first-place finish was in the 5,000 meters and the second-place finish was in the 1,500 meters. In 2009, he set a world record in the T12 10,000 meter event during a race in Galacia.