The Eagles, meanwhile, are expected to get running back Jordan Howard back from injury this week, a source told ESPN's Adam Schefter. Howard has missed the past six games with a shoulder injury.
With Howard set to return, Philadelphia will release running back Jay Ajayi on Monday. Ajayi rushed for 30 yards on 10 carries in three games with the Eagles.
Ertz took a direct hit to the rib area from safety Xavier Woods in the first quarter while attempting to catch a pass. He left for the locker room a short time later but returned to finish the game and ended with four catches for 28 yards.
The timetable for his return to play is still up in the air, "but he's hurt pretty bad," a source said.
"There is a rib that's been affected. I still am waiting on, with our doctors, a couple more tests for some other things," coach Doug Pederson said Monday. "It is [a good sign that he returned to play Sunday]. It just shows his toughness and willingness to go back out there, but as you guys know, we take every injury seriously and make sure that we protect our players."
NFL Network was first to report the fractured rib.
Ertz, who was recently named to his third straight Pro Bowl, ranks second among tight ends this season behind Travis Kelce with 88 catches, good for 916 yards and six touchdowns.
With Ertz ailing, fellow Eagles tight end Dallas Goedert had the best game of his career, posting nine catches for 91 yards and a touchdown in a 17-9 win over the Cowboys that put Philadelphia in the driver's seat in the NFC East. A win at the New York Giants Sunday or a Dallas loss to the Washington Redskins will give the Eagles the divisional crown.