I tried all solutions from Ultimaker website but non of them work.
Here is my solution:
First heat the stucked nozzle to 200-215 degrees. (To melt the material)
Put a segment of PLA material in to the stucked print core/nozzle until it does not go in anymore
Keep the material in the nozzle and apply some preasure
Lower the temperature to 80-90 degrees while keeping the PLA material in the nozzle (To let both stucked material and PLA cool down so they become a whole)
Pull the PLA out and the stucked material should come out
See Picture Below
The pink thing is PLA material I used to pull the material out of course I cutted it, the brownish translucent thing is the PVA material stucked in the nozzle.