Its common to experience both Vertigo and headache post mild traumatic brain injury
.I think you should feel reassured since you already had a neurological examination by your doctor and she did not find anything worrying.
As advised by her vestibular exercises should help and your symptoms should improve over next few days although vertigo post mild trauma can persist for a little while in some.Deterioration is unlikely in patients who have a normal Neurological examination and a normal CT scan.
Some of the worrying signs you might look for are worsening of headaches
,Weakness or numbness
of any part of the body,decreased sensorium etc.Revisit your doctor if you notice any of the above.(the chances of you developing any of these are remote)
Relax & Wishing you a speedy Recovery!