George Kessel, 57, of Pike County was sentenced to two to seven years in jail. Prosecutors said in court his victim may not be the only one.
The victim's grandmother, who is not being identified to protect the child victim, was tearful in court as she asked the judge for justice.
"It's not easy to talk in front of him, but you gotta do what you gotta do, and he had to hear it," the grandmother said.
Kessel pleaded guilty in February to having unlawful contact with a minor.
Police said in November, 2008, Kessel made the four-year-old boy touch him inappropriately behind a restaurant on Business Route 6 in Dickson City while the boy's mother waited on customers inside.
The boy's mother said Kessel was no stranger to the family and was someone they trusted.
"Very emotional. To know my son got, that happened to him," the boy's mother said as she became overwhelmed by emotion. She added the boy, now five, is back and school and doing well but he still remembers what happened.
"Every now and then he mentions something that brings it all back to him. It's on his mind. They say kids forget things. They don't forget these things. These things are with them forever," the boy's grandmother added.
Police in Morris County, New Jersey have charged Kessel with a similar case that happened in 2007.
The boy's grandmother hopes Kessel will serve time for that crime as well.
"I wish we had known about this ahead of time. This could have been avoided. I hope that this puts him away and I hope that maybe this helps other people with their case," the grandmother said.
Those charges, that Kessel inappropriately touched a 12-year-old boy in New Jersey, are still pending.