Person made a statement in front of 3 people that I was thrown out of my son's house because I molested a child

Assuming that the statement was untrue, and that the person making the statement knew it to be untrue when he/she made it, you have a slander claim against that person.  Such a statement would probably be considered defamation per se, meaning that you would not have to show any actual monetary damages to assert your claim.  You should be aware that defamation claims generally have short statutes of limitation (1 year in NY; not sure in PA), so if you want to assert your claim you have to do so in a relatively short time period.