Nelson is expected to hear back from the NCAA on the review sometime in January.
Nelson was having a career season before it was cut short after suffering a torn pectoral muscle against TCU on Oct. 5. Nelson, a defensive captain who finished with 27 tackles, had returned an interception for a touchdown against Notre Dame the week before.
Nelson initially applied to the Big 12 for a medical redshirt, but was denied. He then appealed to the NCAA's Committee on Student-Athlete Reinstatement and was denied again.
The review of his appeal is Nelson's final recourse.
Typically, a player can't have played in more than three games in a season to qualify for a medical hardship waiver. Nelson was injured in Oklahoma's fifth game.
After Nelson's injury, Dominique Alexander replaced him in the starting lineup and earned Big 12 defensive freshman of the year honors.
Oklahoma plays Alabama in the Allstate Sugar Bowl on Jan. 2.