Welcome to Healthcaremagic.
If there was dementia
post injury then the injury should be real hard leading to few hours of unconsciousness
I do not think that it could be due to the injury.It could be stress
involved on mere over conscious about the fact everyone else sees in there day.
Need not worry, If you see it worsening then do consult a Psychiatrist
who can asses and plan a suitable management.
Wish you good health.