you want to make the kalk or pickling lime a paste and just inject some into its mouth, it will shrivel up and melt away. YOu will see a big difference almost immediately and eventually it will all go away. It may have to be done a couple of times though.
If you have none, try your lfs, our one here, if you want some for aptaisia, will give you a little if you ask. Instead of buying a jar of it.