Yesterday i developed sever headache over lt side head, especially my eye, now tenderness over my temple 1 finger above outer part of lt eye.what is it?

See a doctor: Hard to say exactly but if you are having nerve type pain that is constant and tender to the touch, i would be concerned about early shingles (before the rash starts). See a doc soon because, if so, treatment can be started.

Various things.: In a young & otherwise generally healthy person, this sounds like a type of headache like tension/migraine/cluster or sinus issues. Might check if simple meds relieve the symptoms. More rarely, a condition called temporal arteritis may be involved which needs more rapid care. If vision is changing or affected or a throbbing is felt at the temple area or worsening seek medical evaluation soon.