This is something I found growing under my kitchen’s sink. It looks like a growing potato and it’s really hard (tried to pull it down using a hard cardboard but in vain). I think a knife may work but I want to know what this is and if I should be taking any precaution.
I’ve put up a video of it as well here: https://photos.app.goo.gl/JLqJrxeqnboRn9bg8