make sure the thermistor is inserted into the heating block or you will have a runaway heating effect that will make your hot end much hotter than it can stand.
the thermistor could also be bad so make sure you replace that too.
next time you fire it up, keep an eye on the extruder temp and make sure the thermistor is reading the rise in temprature.
you should take apart your heating block and make sure the ptfe tube in the heat throat has not melted. otherwise, if its melted, you will be dealing with clogs and jams.