Hey, I have had headaches for a few days before... nothing to worry about. So many things can cause them; stress, the weather, medications, dehydration, sinus issues, eye strain, neck problems, fatigue, etc.
I had an MRI of my brain because of frequent headaches and ocular migraines, and it came back normal. I wouldn't worry about it, because there are so many other symptoms of a brain tumor besides headaches. People with brain tumors don't always get them, anyway.