"It makes me happy what I am doing, it's a big kindness to myself to keep fighting for my brothers and sisters on Nauru and Manus," he told SBS News.
"I keep fighting for them.
"It was my big dream and I did it."
According to the Refugee Council, as of March 2019, an estimated 360 asylum seekers are in Nauru and 547 in PNG. The council said 508 people had been relocated to the US in March this year.
Kakar has been in PNG since 2013, arriving by boat after he fled Pakistan.
He won a silver medal at the 2012 World Martial Arts Festival but after his rise to prominence says he was then threatened by the Taliban.
He was held on Manus Island until last year and now lives in the capital, Port Moresby.
Kakar said the years he spent in limbo in the detention centre did not break his spirit and the sport was helping him overcome the trauma he suffered.
"I'm doing good things for the community ... I learn many good things in the hard situation," he said.
"The PNG sports field, where they respect me, they give me a chance, they believe [in] me."
Kakar said he still hoped he would one day be granted asylum by any country that would take him.
He found supporters through his boxing, including Australian Anglican priest Dave Smith who campaigns for refugees detained offshore.
Father Smith told SBS News the win is "great news" and he hoped Kakar would continue to fight.