Yes, it is quite normal for many people to get small eyes when they wake up in the morning, so do not worry. The most probable cause of this issue might because you do not have a good sleep last night. For example, maybe you have a dream almost whole night, which means your brain still works and have not get rest while you are sleeping. Or you have suffered from sleep disorder, it is annoying and also affect your metabolism and make your eyes feel tired, which will finally give rist to small eyes. In view of this situation, a good rest is the most essential and available. Meanwhile, you can also put some ices or tea bags on your eyes, it is also a useful way to relieve the symptom. Whereas, if the sympton still exist, you had better ask a professional doctor for help as soon as possible.
The pupil is a hole located in the center of the iris of the eye that allows light to enter the retina. When the amount of light entering your retina are less, your pupils are easy to be small. Everyday when you wake up, your eyes have already lack of light for 8 hours at least. So it is naturally and normal that your pupils are so small.
I guess that you must not wake up completely from your dream that make your eyes look smaller. Falling asleep won't cause smaller eyes. ON the contrary, sleeping is good for your eyes as well as your body. So, don't worry, it won't make your eyes smaller and smaller in the future. Also, if you want to make your eyes look bigger, you can wear eye makeup to enhance your look, for example, you can apply eyeliner, mascara as well as eye shadow to make your eyes look bigger.