Pain in only one eye can happen for many different reasons, including eye strain, dryness, infection, allergy, sinus pressure, migraine, corneal irritation, increased eye pressure, or inflammation inside the eye. Sometimes the pain may feel mild and irritating, while in other cases it can become sharp and throbbing, or be associated with redness and blurred vision. The exact cause usually depends on whether symptoms like watering, headache, swelling, or sensitivity to light are also present. Giving the eyes enough rest and reducing screen exposure for a while may help if the discomfort is due to strain or dryness. Dust, smoke, strong sunlight, and repeated rubbing of the eyes can worsen irritation. Avoid using random eye drops without medical advice because some drops may temporarily hide symptoms while the underlying condition continues to worsen. Lubricating drops or other treatment may sometimes be advised after proper examination, depending on the actual cause. A proper eye check-up would be safer if the pain becomes severe, vision turns blurry, redness increases, or headache and vomiting start along with the eye pain.