Someone accidentally hit me in the head i was fine no loss of consciousness or any major symptoms but after 3 days i'm having a headache could it be related? is seeing a dr necessary for my case?

Any blow to the head can have potentially problematic results. If you are having a new onset headache, it could be indicative of a concussion or less likely a brain bleed. Call your primary Dr and discuss with them as related to your specific medical history. They may want to see you to run a complete neurological exam or they may give you precautions to take instead.

Based upon your description, you did NOT have a concussion, skull fracture, or an intracranial hemorrhage, but post-traumatic headaches can follow even mild closed head trauma. Would contact your doctor about the headache. If it gets worse, you develop nausea, vomiting, dizziness, imbalance, blurring or doubling of vision, then these signs indicate need to see doctor ASAP.