"I'm fine," Johnson said on a teleconference Monday. "I'm very fine. I'm good."
Johnson, one of the top running backs and all-purpose runners in the country, was shaken up during the first quarter in Chapel Hill.
"I was trying to throw a block, the guy moved at the last moment, took a knee to the head," Johnson said. "Came back the next drive and kind of felt a headache coming on because I suffer from headaches, so I went to the training staff after that."
Johnson said he has a history of migraines.
"It's something I've been dealing with for a while now," he said, adding that his mother also suffers from them. "I'm just trying to get them under control with the training staff, get them under control so I can play without having to worry about it."
Johnson leads the team with 655 rushing yards and four touchdowns this season. He is averaging 7.1 yards per carry and 109.2 yards per game. He has 3,097 career all-purpose yards and is on pace to break Santana Moss' Miami record.