Jack Nelson attended high school at Stoughton High School in Wisconsin, where he was a decorated offensive lineman on the football team. Nelson was a four-star recruit by ESPN and Rivals and was given the Joe Thomas Award as the state's top senior offensive lineman. Nelson also was a three-year letterwinner in basketball and a three-time high honor roll student. Although he had several offers, Nelson decided to stay close to home, committing to the University of Wisconsin.
Nelson took a redshirt in 2020 after only playing in one game for the Badgers. As a sophomore, he started all 13 games at right guard and helped pave the way for the No.2 rushing offense in the Big Ten. He switched from guard to left tackle in 2022 and started all 12 games, recording a 83.1 pass blocking rating via PFF. In 2023, Nelson started in all 13 games at left tackle.
Nelson started all 12 games in 2024 and at the end of year he accepted an invitation to the Senior Bowl.