"There's some pain," he said a few hours after his spectacular grab on Denard Span's first-inning drive to deep center sent him crashing up against the wall. "Not sharp but a little more than dull. What happened was the lower rib-cage bone and the hip bone hit each other when I was pushed up against the wall."
Heyward will have an MRI performed on his right side Saturday to determine if there is any structural damage.
"Luckily, nothing is broken," he said. "We'll see how it feels tomorrow after the MRI."
Kris Bryant, who drove in four runs, three on a second-inning home run, called it the play of the game.
"It was a little strange after the first out," Bryant said. "Jason's catch, it was unbelievable. It set the tone for the game. That's a mentality. He's the best defensive outfielder in the league and he gives his all. He showed what kind of player he is on that play."
Heyward said he tracked the ball all the way.
"There was a long way to run," Heyward said. "There was a lot of space, enough to make the play. You try to slide in a way you don't land on your wrist. The momentum took me to the wall."
Heyward walked off without help from athletic trainers who had attended to him in the field, though he grimaced most of the way in.
Tommy La Stella entered the game at third base, with Bryant moving to right field.
"It's unfortunate it had to happen that way," Cubs starter Jake Arrieta said. "He put his body on the line to make a play. His ability to stay focused on the ball while traveling at a high speed with no regard for the wall ... he's the best in the league."
Cubs manager Joe Maddon was staying positive.
"We don't know anything for sure," Maddon said. "But you could see in his face that it was bothering him a little."
Rick Eymer is a contributor to MLB.com and covered the Cubs on Friday. This story was not subject to the approval of Major League Baseball or its clubs.