Just visited my eye doctor, he said my eye nerve a little bit swolled.he told me to rest and avoid direct sunlight. actually, what cause it?sunlight?

Swollen eye nerve ma: A swollen eye nerve may be a sign of other problems, some i assume he meant a "swollen optic disc". It could mean elevated pressure inside your brain (causing papilledema, and if associated with headaches, other signs suggest benign elevated intracranial hypertension. Or more serious, like obstruction or aneurysm. You should ask if you need further testing, or a consultation with a specialist.

Not normal: A swollen optic nerve is not normal and needs evaluation. It could be a sign of many problems, some of which are life threatening. See an ophthalmologist soon for evaluation.