Mac mini

Try holding down the left mouse button while powering on the Mini which should eject any discs from the optical drive assuming the optical drive is still working. Make sure to use a wired USB mouse. If this does not work, then most likely the optical drive is jammed or broken.

That indicates the optical drive is bad since the internal mechanism is either jammed or out of alignment. You can use an external USB optical drive instead which will be easier than trying to replace the internal optical drive as that involves completely removing everything to get to the internal optical drive.

Blocked how? What happens when you try to use it exactly?

Is there a disc inside? Have you tried to eject it?