Let me tell you this way - one of my fish broke my glass thermometer
in 30g tank. Smacked it onto the glass wall with the tail...
It was not a small crack - it was completelly crushed and
fall into the sand the way I could not find all the glass pieces or
the metal weights dipped in the red wax (from inside thermometer).
I siphoned out the sand from the corner thermometer fall I had
no bad symptoms suggesting any poisoning... You will be good.

p.s.
I learned not to use glass thermometers.
I use electronic ones with plastic probes...