Is it there in both eyes Is it on either side of the cornea It could be Bitot's spots as you say there is no discomfort, in which case it's quite harmless. It's a sign of vitamin A deficiency

Picture of the eye will be helpful to comment. Follow these general to reduce eye strain 1.Frequent blinking of eyes 2.For every 20 minutes look far away for 20 sec 3.Drink more water 4.Do not sit in front of air conditioner 5.Take Adequate break in between 6.computer screen should be 16-30inches away 7.ensure the screen is neither too bright nor dim 8.get good sleep 9.use lubricating eye drops 6 times per day 10.ensure there is no glare from your screen.

Difficult to comment without seeing it Probably some normal degenerative change Try to restrict phone use for longer time. Use lubricating drops