Well, it can be normal to have this kind of situation. So you do not need to worry about it. Generally speaking, there are many reasons which can lead to dilated eyes. For example, high blood pressure and anxiety can lead to it in some degree. So when you have high blood pressure, it can just affect your eyes, and then leading to dilated pupils. But maybe the high blood pressure only affects one eye, and that can only cause one eye dilated. Also, you should know that drug use, illness, and trauma can cause it too. Anyway, for your situation, just go and see the eye doctor as soon as possible.