As the PVA has been carbonized, the carbon will not dissolve in organic solvents. Actually, don't use acetone as any PVA residue will dissolve easily in water. You may be able to loosen the residue (if there is still some PVA left in it) by boiling it in water with a little dish washing detergent added. Rinse and dry thoroughly aftwerwards. If you have an ultrasonic cleaner, you could try that as well, it might shake stuck carbon particles loose.

My suggestion would be to exchange the nozzle and ptfe tube for new ones. It does not cost that much, and quickly outweighs any cost in losses of failing prints in the future due to remaining small particles dislodging and clogging the nozzle. It is wise to just order spares from china anyway to have them in stock. There is no rocket science in a brass nozzle or a piece of PTFE tube, and those few bucks will save you a lot of grief.