you could go to the police to file charges but that will not change your child support. hiring a lawyer and doing a motion to vacate the last order may modify your support.
Sounds like a 1401 motion to vacate for fraud.
BUT depends how much time has passed and what due diligence was used. By way of illustration, if this event happened 2 years ago and you just now decided to do something about it, judge may think it's fishy that you waited so long.
But if it JUST happened and you act ASAP, different story. Talk to a family law attorney in your area for specific guidance.