Nichols graduated from the United States Air Force Academy in 1979. From 1989 to 1991, he was stationed at Torrejón Air Base in Spain and served in the Gulf War before being assigned to The Pentagon. In 1992, Nichols joined the Wisconsin Air National Guard and was assigned to the 128th Fighter Wing. From 1994 to 1998, he served as Operations Officer of the 176th Fighter Squadron before serving as an operations group commander at Truax Field Air National Guard Base in Madison, Wisconsin for two years. In 2000, he was named Vice Commander of the 149th Fighter Wing of the Texas Air National Guard. From 2003 until 2009, he was in command of the 149th Fighter Wing. He was named Assistant Adjutant General of the Texas Air National Guard in 2009 and stayed in that position until becoming Adjutant