The Ninth Commandment reads:
Thou shalt not bear false witness against thy neighbour.
The problem with bearing false witness that harms a neighbour is that you then cannot earn the Kingdom of Heaven.
It does not matter that the harm is minuscule as long as the lie did cause harm.
Harm not only deals with monetary loss or destruction of property caused by the lie, but especially if it deals with the destruction of the persons reputation.
Then is the person who bore false witness condemned to hell for eternity? Not necessarily.
To regain his salvation the false witness must undue all the harm that was caused to the person. Must contact everyone that heard the lie and confess to them of the lie.
It is not sufficient to merely correct your lie but must also correct all the lies told by everyone involved in the incident that you know about. Even then it is not sufficient.
You must make positive that all the harm has been undone.
(Also see my post of 2/2/13 re. You Lie For Someone Else).