I hit my head on the car door frame yesterday.had a lil headache yesterday, this morning woke up with a bigger headache should i go to er to get check?

Probably: If the headache i much worse or dramatically worse and is associated with focal weakness or sensory loss, definitely need to have this checked out.

Yes or a neurologist: You could have a concussion or even something more serious. It is important to be seen and evaluated. If you cannot see a neurologist within 24 hours it is best to go to an er.

Peace of mind: Sure. Go to the er and they will make sure that all is well. Hopefully it is just a bump but it could be something more and it would be good to catch that early. Peace and good health.