I’d use a correctly sized pin punch to gently knock it out of the socket. Measure the hole and buy one from your local hardware store (slightly undersized is ok) then clamp the hot end down securely with the thermistor set so you can use the pin punch to carefully and gently drive it out into a void down below. Gentle taps with a hammer should do the trick.
If that doesn’t work, you could potentially try drilling out the middle of the thermistor, then using a small coping saw to cut the thermistor from the inside to the outer edge and then remove the carcass with a pair of pliers. It might honestly be easier to just buy a new heater block at that point, and with significantly less risk of damage!