A nib is something small that comes to a point. Originally it was the tip of a quill pen, and now is commonly used to describe the metal piece at the end of an ink-well pen or the tip of any writing instrument. It may also mean a bird’s beak or bill.
In cooking, a nib is a small piece of a roasted product, like coffee or cocoa beans. It is always used in a compound form, such as, cacao nib or coffee nib.
A nub may also mean a tiny piece that projects or sticks out, though not generally coming to a point. It may be used as a synonym for gist or essence of a problem.
Other synonyms for a small projecting piece can be nubbin, knob, or lump.