I would first point out that the age of consent in both New Jersey and Pennsylvania is 16 years of age, so sexually explicit conversation or even interaction between someone age 16 and up and an adult is not illegal as long as the participants are both located in either state.
Secondly, even if the minor was in a different state, the resources that it would take to track you down would be tremendous. Furthermore still, they would have to prove beyond a reasonable doubt that it was actually you involved in the conversation.
Third, the minor would actually have to be a minor, and actually have to report the crime(if it was a crime).
So the risk factor is very low--virtually zero. Learn from this incident, but I would not worry at all.
I understand that you may have follow-up questions. Let me know if further clarification is needed, and please keep in mind that the experts are not credited for unaccepted answers; even where I cannot solve every problem in a case, my hope is that you can at least feel confident in your knowledge of your rights so you can get the best legal outcome under the circumstances, whatever that outcome may be. Thank you.