Hi NearThere,
grain of salt
(With) a grain of salt is a literal translation of a Latin phrase, (cum) grano salis. A pinch of salt may also be used.
In common parlance, if something is to be taken with a grain of salt, it means that a measure of healthy skepticism should be applied regarding a claim; that it should not be blindly accepted and believed without any doubt or reservation. According to the Oxford English Dictionary "to take 'it' with a grain of salt" means "to accept a thing less than fully".
Regards.
V.