Nygren is a fourth generation resident of Northeast Wisconsin. He graduated from Marinette High School in 1982, has studied at the University of Wisconsin-Marinette, and worked in the restaurant industry for over twelve years, eventually becoming co-owner/operator of his own establishment. In 1998 he started work at Great Lakes Financial Management Group selling insurance and other financial services.
Nygren was very involved with the Jaycees. He served as Marinette's Chapter President, the Regional Director for Northeast Wisconsin, Wisconsin State President, and the United States National President.
Nygren served as the Chairman of the Marinette County Republican Party, and served on the City of Marinette Recreation and Planning Board from 2003–06. In the September 2006 primary election to succeed fellow Republican John Gard for the 89th District (Gard was running for Congress), Nygren narrowly defeated Gary Drzewiecki, with 2777 votes to Drzewiecki's 2740, and went on in November to defeat Democrat Randy Koehn (a Marinette High School teacher, as is Nygren's wife Maggie), 11,844 to 10,011. He was assigned to the standing committees on insurance, education, health and health care reform; and jobs and the economy
He was unopposed in the 2008 Republican primary, again faced Koehn in the general election, and again defeated him, 14,814 to 12,839. In 2010 he was again unopposed in his primary, and defeated Democrat Bob Orwig by 15,788 to 7,520.
In 2011, Nygren sought to run against incumbent Democratic state senator Dave Hansen, who was the subject of a recall election; but the Wisconsin Government Accountability Board ruled that he was two signatures short of the necessary 400 signatures on his nomination petition, and would not be on the ballot.
In 2012 Nygren was unopposed in the Republican primary and defeated Abrams Town Chairman Joe Reinhard in the general election 59%–41% (16,081–11,129).
In 2014 Nygren was unopposed in both the Republican primary and general election, taking 99.38% of the general election vote.
Nygren is married to Maggie, a family and consumer education teacher at Marinette High, and they have three children Cassie, Cali, and Colin. The Nygren family is active at Faith Lutheran Church, where Maggie teaches Sunday school and chairs the Mission Board. John now serves as church Elder, and previously spent four years as Church President.