see stars

verb2

1. •
   To experience apparent flashing lights in one's field of vision, especially after receiving a blow to the head.

   • Of course they bumped their heads smartly together, saw stars, and both came up flushed and laughing, without the ball, to resume their seats, wishing they had not left them. — 1868
2. •
   (figurative) To be reeling immediately after a sudden misfortune analogous to a blow.