In an interview with PEOPLE for its latest cover story, the actor revealed he filmed 2016’s Hidden Figures while secretly suffering from kidney stones, and worked for two weeks on morphine.

“I’ve never worked drunk on a set. I’ve never worked high on a set, but I was on morphine the last two weeks that I worked on [Hidden Figures],” recalled Costner, 69, who played Space Task Group director, Al Harrison, in the film, which follows the true story of three African-Amerian mathematicians who worked at NASA, and their brilliant work to help the US during the Space Race.

During the film’s shoot, Costner said he learned he had kidney stones, which can be extremely painful.

“[I] worked 10 days under an IV drip. I don’t even know how. About three days of it I was normal and then something happened to me,” he told PEOPLE, adding that he “never missed a day of work.”

“I sat in my trailer with a morphine drip in my arm,” he recalled.

The Oscar winner went on to share that he had to keep his shirt sleeves rolled down in order to hide the bruises he got from the IV drip.

“Eventually I had to,” Costner said, admitting that battling kidney stones was painful. “I wanted to cry, but there was everybody watching, so I didn’t.”

This comes just a few days after Costner’s 15-year-old son praised his dad’s work ethic at the premiere of his film, Horizon: An American Saga, and caught Costner off-guard with his sweet comments.

Hayes, who plays Nathaniel Kittredge in the film, was excited to be alongside his dad — who directed, produced and stars as lead character Hayes Ellison, named after his son — at the movie’s premiere on Monday night.

“He trapped me,” Hayes joked to Entertainment Tonight about the extra time he spent with his father on set. “I got to spend the whole day with him every day and just see him work … I had such a blast.”

“It was so fun. Just working with my dad, I loved it” Hayes continued. “It was amazing to watch him direct because I’ve never seen it before.”

When asked how it felt to hear his son talk about him like that, a teary-eyed Costner said, “It feels good” — appearing to get choked up before taking a moment.

As the interview continued, he also jokingly put on his sunglasses, to hide his emotions.

Horizon: An American Saga Chapter 1 is in theaters now, and Chapter 2 will follow in August. Chapter 3 and Chapter 4 are still in production.