What are the lights I can see when I poke my eyeballs accidentally?

Entoptic phenomena. The retina is the sense organ of the eye. It responds to light and sends a signal to the brain, which is interpreted as an image. The retina can be made to send a signal when it is compressed, such as when you push on your eye (not recommended). The signal gets interpreted as light in the brain and you "see" lights that aren't present. This would be considered an entoptic phenomena.