It could be floaters in your eyes. They will become less noticeable as time goes by. As long as they don't affect you vision, there is no problem. The only thing you should do is trying not to notice them. If they annoy you a lot, then you should go to see a doctor.
It mightbe a visual aura which is related to a type of migraine. I would suggest you visit a doctor to have an eye test. The doctor will check your vision and your eye health to make sure they are in good condition.