My Pilot Metropolitan came with a cartridge, now clean, dry and empty – except for one thing: a tiny black plastic something inside it. Perhaps it was a sealer, but I didn't really notice when I first used it. Can I just pry this out with a toothpick, or is it a necessary part of the cartridge that got dislodged. Is my cartridge now useless? Picture attached. Not great quality but gives idea. Thanks for help. This site is invaluable.