"The courts have for a long time now made it absolutely clear that this sort of violence on the field of play cannot and will not be tolerated," said Judge Robert Brown during sentencing at Preston Crown Court.
"And for this kind of off-the-ball incident a custodial sentence is inevitable."
Cotterill is banned from football until March 1 following the incident, and has also resigned from Barrow.
The Barnsley-born defender began his footballing career as a trainee at Glanford Park, making 24 appearances before being released in the summer of 2003.