PLA is not acetone-soluble, so that wouldn't help anyway. To remove PLA from the nozzle, heat it to 90-100C (too hot and the PLA will be liquid and won't lift out) with the filament in it, then slowly pull the plastic out. It should stretch into a thin string. Try not to break that string, and you might get it all (you'll be able to see a nozzle-shaped piece at the end if you're successful. If it doesn't work, you'll have to heat it up to extrusion temperature and try pushing the filament through for it to bond so you can try again, or you can remove the nozzle with a pair of wrenches (one on the nozzle, one on the block) while it is still at 100C. Have a paper towel or rag ready to hold the nozzle tweezers and a pin to dig the plastic out before it cools. When putting the nozzle back, make sure it tightens down hard against the barrel, not the heater block. There should be a small (less than 1mm) gap between the hex part of the nozzle and the heater block when it's tight.