(CNN) In September, Stephen Martin saw a Nike ad featuring former San Francisco 49ers quarterback Colin Kaepernick.

The ad said: "Believe in something. Even if it means sacrificing everything."

The words "sacrificing everything" stood out to Martin. And he decided he needed to take a stand against Nike.

He sold off the Nike inventory in his Colorado sports apparel and memorabilia store, Prime Time Sports, and made national news as the store owner boycotting the biggest name in sports merchandise.

Martin knew the Nike boycott would hurt.

"Being a sports store without Nike is like being a gas station without gas," he said.

This week, Martin announced that Prime Time Sports will close in the coming days.

"This was never about property to me, this was about principle," Martin said Wednesday night while he was in his store, preparing to shut it down.

Martin said the boycott was about principle over profit and even though the lost revenue played a role in his decision to close the store he was absolutely glad he did it.

"You don't trample over the men who have given Colin Kaepernick and me the right to free speech," he said.

The former NFL quarterback became a polarizing figure after he began kneeling during the National Anthem during the 2016 season to raise awareness about police brutality against African-Americans and other racial injustices. Dozens of other players joined him and he has become a symbol of the dividing lines over race in America. Some called kneeling during the anthem unpatriotic and disrespectful. Kaepernick has not played in the NFL since the 2016 season.

Nike's decision to use Kaepernick to promote the 30th anniversary of its "Just Do It" advertising campaign outraged some sports fans, including Martin.

In 20 years in business, Martin said he thought of himself as a guy who sold jerseys, not as an activist. He had never boycotted anything before, though in 2016 he canceled an autograph appearance by Brandon Marshall after the Denver Broncos player took a knee during the National Anthem before a game.

This week, with past due rent bills portending a court fight he decided to tell his nine employees it was time to call it a career. Everything in the store is 40% off.

Other stores in the mall, including a Sears, are closing. Mall traffic is down.

Martin told CNN affiliate KOAA that his sales had also been affected by people buying more items at online retailers. His sales were down 15% in the past three years.

The store will be open until everything is gone, he told KOAA.

"I didn't give in to big Nike and big dollars. I didn't give in. I did it my way," he told the Colorado Springs station.