Bryant's head appeared to come in contact with Heyward while the two tracked down a fly ball off Eugenio Suarez's bat.
After the collision, Bryant spun to the ground and was slumped over in obvious pain before the Cubs' medical staff came to him.
He left the contest under his own power, and Albert Almora replaced the two-time All-Star. Cubs manager Joe Maddon said after the game Bryant is under evaluation, according to MLB.com's Jordan Bastian.
"He's doing OK. He's still under evaluation," Maddon said, according to The Athletic's Patrick Mooney. "We don't know exactly what we're doing with this whole thing yet. But we're trying to talk with the docs and him to find out exactly where we're at."
Although his status remains in question, Bryant was cleared to fly with the Cubs to Houston for their upcoming series against the Astros, Mooney adds.
The 27-year-old, who's usually the team's third baseman, has played right field 11 times for the Cubs this season.
Bryant entered Sunday hitting .288/.411/.576 with 12 home runs and 34 RBIs in 2019.