My son is 8, , gets sudden headaches in the evenings and he cries, holds his head until he goes to sleep. When would CT be in order. Doc not worrie?

Eyes checked. Evening headaches can be visual, also trat the sinuses with flonase. He sounds miserable, i would get a second opinion, ct would be recommended but frequently one finds nothing. Could be migraines but vision and sinus top of list.
Needs evaluation. His symptoms could represent many things. Migraine, seizures, tumor, etc.. His doctor is in the best position to diagnose him. Mri is preferable since in involves no radiation. But a complete work up is needed not just contrast studies. Please check back with your doctor to express your continued concerns.