Williams was injured on a Colts' punt in the first minute of the second quarter in the 25-13 loss. He was strapped onto a stretcher and carted off the field at Lucas Oil Stadium before being taken to an Indianapolis hospital.
The 30-year-old Williams returned to the stadium after being released from the hospital and Colts coach Chuck Pagano confirmed the tight end was back with the team's medical staff.
"It was a pretty scary thing ... but he's back here," Pagano said after the game of the fifth-year player. "He's doing well."
The Colts said Williams did not suffer an injury to his neck. He received a standing ovation from the crowd and well-wishes from his teammates before being driven off the field.
Williams suffered the injury while blocking Broncos linebacker Deiontrez Mount on the punt as the two players collided.
The 6-foot-3, 260-pound Williams has 13 catches for 121 yards in 14 games this season. He played for the Carolina Panthers from 2013 to 2015 before a brief stint with the Miami Dolphins. He signed with the Seattle Seahawks last season. His college career at Oregon came to an end a year early because of a spinal condition.