A couple of question for you:

Have you ever had headaches before?
Do you have allergies?
Have you had your blood pressure checked?

Pressure could be an allergy, or just the beginning of a cold, but if you doesn't go away soon, see your own doctor and he/she can give you somethink for it. If you're under stress or upset about anything, that can cause some of the headache as well.

Take care