Mystery! Cd unit

Hi all, I hope someone can help me please. I had to take my battery out to charge up, put it back, starts fine. But, now the Bose cd unit won’t play, message says “check cd” I pushed the knob to take the cb’s out it did 5 of them and has kept the last one! Any ideas would be great, thanks.

From my experience, you’ll probably have to remove the audio unit from the dash, take the top of it off and try and coax the remaining CD out by plugging it back in “open” and looking at what’s happening inside.