The light flash is from stimulation of the retinal cells, usually when the eye muscle insertions exert a little pressure through the eye and one sees light. This is normal.
If you move your eyes around fast you will see a little light show in the dark.
Regarding a CD light, no problem although I would not make a practice of looking at any bright light for very long.
One more question please. I read a question from someone who asked if looking at a laser on a computer mouse could damage your eyes. Several years ago my portable CD player quit working and I opened the top to wipe off the lens, but I didn't really look down into it, or even look at it but a second or two.
From your answer to the other person there is no danger, so that should apply to me also, correct?. I've never noticed any difference in my vision since then. And it was just a little portable CD player, someone told me they automatically cut off when they are opened anyway.
So there should be no danger?