I would ask my doctor if drinking will affect the healing of the head trauma. They might be wanting to keep you around for a while to allow the injury to heal without alcohol. alcohol use is not recommended when your body is healing from any serious trauma.
On the other hand, I don't think forced rehab is a very good solution.
My brother has had serious head trauma including stroking from injuries suffered while drinking.
It's not something to fool around with: he has permanent memory loss. His injury was also acquired during a stint of severe alcohol poisoning.
I'd try to get better first, before having a drink!