The current state of the law, as well as the philosophy of many prosecutors is very aggressive with regard to child pornography. Without knowing more about the nature of the call or how you came to view the web cam images, I can't advise you about whether they will approach it as the report of a concerned citizen or as an anonymous confession. Even turning over a copy of any saved video file could be couched either way.
With regard to the anonymous nature of the call, there is usually an exception if the Social Worker believes that disclosure can prevent further or more serious abuse.
You need a competent attorney experienced in federal and state matters to advise you on this.
Under PA law, the identity of the reporter (called referral source) of suspected child abuse is highly protected. Any disclosure in PA is a crime graded as a misdeanor. On the other hand, development, product or possession of child pornography is an extremely serious situation. You should not delay, and go consult with and retain an attorney!
If there is none, you have nothing to worry about. The more important question is how you came to view the act that you reported. It probably didn't pass the police's sniff test. I am sure there is more to this story. You should consult with a criminal defense attorney who is experienced in sexual abuse cases. Call us at 215-625-4547 for help.
Carina Laguzzi, Esquire