Since your eye is not red and you have no gritty feeling in your eye, I think it might be a corneal abrasion. You should go to see your doctor right away. Tell him you your problem you have and he will give you a careful exam to find out the exact reason.Then he will take measures to treat your problem.
Sore eyes could simply be an indication that the eyes are tired for some reasons but sometimes, it is a symptom of an eye disorder. The best advice is to see an doctor and find out the true reason of sore eyes.