Since you don't specify the model, you are unlikely to get a comprehensive answer. Check the user manual for "manual disk eject" or something similar. On some trays, there is a pin-hole you can insert (e.g.) an unfolded paper-clip end into, which manually unlocks the tray, but this is not universal.
Best bet is to consult the manufacturer's documentation.
Sparks (the Plumber)
We may have found other answers which could help you.