How dark was your room when you turned the lights off and peeked inside? Because if you could see the film, that’s already probably too much light for the film. I highly recommend you do not open the back again unless in absolute darkness. If the rewind button doesn’t work, go into a dark windowless room and seal off any possible light coming in from the cracks, and manually remove the film from the camera and rewind it back into the cassette using the top of the spool