Hall severed his septum in a challenge from Leon Best whose stud caught the defender in the nostrill.
"It was a freak accident and the lads were taken aback by it," Coleman said to BBC Coventry & Warwickshire.
"There was a lot of blood and I was convinced he'd broken his nose at first but when (physio) Michael McBride took a closer look it seems he's severed his septum.
"I cannot see him being available for Saturday such was the severity but we will wait and see what the verdict is after he has been to hospital.
"It's a real shame for the lad because he has being doing a great job for us in recent weeks - especially with so many other players out injured. We are all keeping our fingers crossed for him that he makes a speedy recovery."