I’ve done 1 print with an ender 3 s1 plus (with sprite extruder pro) and saw this built up on the side of the extruder. The printer still printed fine and began to heat up normal except this time it was “dripping” filament through the nozzle. What is this build up on the side of the extruder and what course of action should I be taking here?
I think you will find the nozzle has come loose from the hotend and is leaking melted filament.
You need to proceed with caution, it is very easy to damage the temp sensor and heating element cables.
May be best to remove the whole hotend and work slowly on bench/table, you will need to heat with a heatgun if possible to loosen the filament.
Alternative is to buy a complete hotend assembly.
How would I prevent the nozzle coming loose in the future?
the general consensus is to preheat the hotend, then screw the nozzle in ensuring it is tight. Make sure you hold the hotend with a spanner whilst tightening the nozzle. Also, try not to burn your fingers. I am sure there are tutorials on Youtube.