When you're feeling a headache on the top of your head the headache on the top of your head is likely just a tension headache that should go away after awhile.
When you have a tension headache the tension headaches cause a constant pressure or aching around your head which can feel like a tight band has been placed around your head.
Tension headaches are usually nothing to worry about unless they get worse or don't go away within a day or so.
I had a headache on the top of my head and went to the doctor and told them about it and the doctor said it was just a tension headache.
You can try applying a warm compress to the top of your head or an ice back and take some aspirin or other pain medicine to help alleviate the tension headache.
If the tension headache comes back too often or it doesn't go away within a day or so or gets worse then I would see a doctor about it just to make sure nothing else is going on.