According to the Fort Worth Star-Telegram, the NFL ruled Dixon struck "a defenseless player in the head and neck area."
Dixon was selected in the seventh round of this year's draft out of Baylor. He is listed as the Cowboys' third strong safety.
Dixon earned First Team All-Big 12 and First Team All-America honors as a senior.
Dixon will be allowed to appeal his fine, as it is larger than 25 percent of his weekly salary.
- Dan Gartland