Yeah, it is totally common. Apart from rubbing your eyes, when you just make your eyes exposed under the strong light, you will find that you can see some stars. As we all know if you do the two things above, you are pressing on the cones in your eyes, when your dear eyes will be activated by pressure or by the strong light. And then the message go through your brain that the cones have received a signal, which has been activated, finally your brain tells you that you see the beautiful stars. At the medical field, there is a term to describe it-- pressure phosphene. At some time, it is a little uncomfortable, if you want to clear the problem, you can just close your eyes and open them again, and then the pressure phosphene will disappear. In a word, you should make your eyes have enough rest and if the problem still annoys you, you can go to hospital to ask the doctor for help. Good luck.