"It wasn't anything serious," Self told ESPN. "He'll probably miss a week."
Ellis played 17 minutes in Kansas' 76-69 home victory against West Virginia on Tuesday night before suffering a knee injury late in the first half when teammate Landen Lucas fell on his leg.
Ellis underwent an MRI, which showed that he suffered a sprain.
He is averaging 14.2 points and seven rebounds for the Jayhawks, who clinched the outright Big 12 regular-season title with the overtime victory over the Mountaineers.
Kansas Needs OT To Beat West Virginia
Kansas topped West Virginia 76-69 in overtime to clinch the Big 12 regular-season title.