What will be the best way to remove pla from a volcano nozzle?
If you grab the blob with a pliers and twist, all or most of it may pop off.  If not,  heat the extruder up perhaps 10 degrees higher than usual, and wait for the external gunk to soften up and then pull it off.
edit :
Well, if it won't get hot enough, then try using an external source such as a soldering iron tip to cut off most of the mess, then it may be time for exacto knife blades and small files to remove the remainder.
Unless you're a clean freak :-) a little residue around the nozzle doesn't matter - it won't touch your prints and at some time in the future it'll be &quot;cooked&quot; enough to fall off.