A clogged nozzle is the second-most-common reason a printer that used to work suddenly doesn't. The fix is almost always one of three procedures: a cold pull (free, 10 minutes), a nozzle change (cheap, 15 minutes), or a hotend rebuild (last resort). Knowing which one you need is the entire skill.
Try a cold pull / atomic pull first — it solves 70% of clogs and costs nothing. Heat to 250 °C, push in a stiff filament (nylon or cleaning filament), cool to 90 °C while pushing, then pull out fast. Whatever was stuck comes out clinging to the cooled filament. If two pulls don't fix it, swap the nozzle — nozzles are consumables, not lifetime parts.
Before you tear into the hotend, rule out look-alikes:
The standard procedure for clearing a partial clog without disassembly. Works on every FDM hotend.
If cold pulls don't fix it, the nozzle's threads or orifice may be permanently fouled. Nozzles cost $2–$10 each — cheaper than the time you'll spend trying to clear a stubborn one.
These printers ship nozzles as full hotend assemblies . The whole hotend pops in/out as a unit — faster and safer than separating the nozzle from the heater block.
Last resort, only when filament is wedged in the heat break (the narrow tube above the nozzle) and won't budge.