Not good at all .... hope you are on the mend and everything heals well.
It is easy to think that a sanding machine cant to too much damage. I was stupid enough when using the disc sander to hold thin pieces in my hand ..... didn't take long for the timber to fly off leaving me pushing my fingers directly into the spinning disc. First time was ok as it hit a finger nail grinding half off ..... stupidly I tried again and the next time quite a lot of my finger top went missing. Fortunately it was clean and didn't require any medical attention ..... just a few weeks to heal.
I now make sure that I have push blocks ......
Sorry to hear your tale but a good reminder for others.