I always see stuff like that when I close my eyes, but not while inside a dream. Could try looking away, or go into a dark place, or bright place, spin around, or going into a mirror or something. If you still see it maybe try blinking, if you do it to often though might wake up.

Oh maybe walk outside and stare up at the sun, hopefully you wont go blind inside the dream, if your worried don't stare to long heh.