Ender 3 V3 KE burning smell

Hi all - bought an Ender 3 VE K3 just under 6 months ago and have used it sparingly i.e. have only gone through about 1kg of PLA filament. Haven’t made any changes to it since setting up.

I’ts now just started to give a burning smell when heating up - has anyone any ideas/suggestions on what I need to check to figure out what the cause is?

Can’t see anything externally on the printer that could be causing it.

Cheers - Mike

Left over filament on the nozzle under the silicone sock?

Thanks Bonfireman - yes, baked on filament all around the nozzle housing. Will see if I can figure out how to get it cleaned up.