First to remove the material, pull on the filament below the feeder while it is removing material. You might need to remove the bowden tube if the filament is stuck in the printhead(happened to me)
To clean the nozzle, follow these instructions:How to clean out the nozzle of an Ultimaker 2 3D Printer
(1) First buy yourself some of these great little strong syringes !
(or amazon.com, but eBay is cheaper. https://www.amazon.com/gp/product/B