Heatcreep (how to prevent) :
Blocked Nozzle : This is very common.
Easiest way to clean it is with an airbrush needle or more fiddly you could dismantle your hotend.
Why does heatcreep occur? Most commonly, printing too fine layer heights too slow – filament moving through hotend too slowly softening filament in the “cold zone” . Another cause of blocked hotend is too much retract distance – pulling soft filament into the cold zone. For Multimaterial hotend also check your tool change retraction distance. If you have an NF TC02 hotend, reduce your tool change retraction distance to 34mm.
I’d also bet you have a lot of chewed filament in your bowden tube. Preheat your hotend and remove and discard all the filament in your bowden tube before attempting to restart any prints.