He walked out of the office under his own power and was driven to UNC Student Health where he received the five stitches.
At the time of the incident, Williams was ready to appear on ESPN Radio at 1:45 p.m. with Mike Tirico and Scot VanPelt, but he was unable to make that appearance. He also canceled his weekly press conference with the North Carolina local media that was scheduled for 2 p.m.
He returned to the Smith Center at 3:15 p.m. in time for Friday's practice.
The No. 1 ranked and unbeaten Tar Heels (16-0) play host to NC State (11-3) at the Smith Center on Saturday at noon (ESPN).
"Oh yeah, must have been like 36 stitches and the doctors say Wanda (his wife) has to make me a home-cooked meal," Williams joked to reporters upon his return to the arena.