This problem you are describing can be because of the injury
which you may have during the brusing as you told that you brush a little too far back. If anyhting visible injury is there than it was most likley due to that only.
The oral cavity is very sensitive and if anything goes wrong with the oral cavity than it can be felt in the head also.
I would suggest you that you should wait for some time and if this is not relieved than have a consultation with ENT surgeon to make sure that there is no severe injury which may be causing this.
Thanks and take care.