I am court ordered to keep my child on my med. insur. I recently became aware my ex has him on medicaid. Can I be penalized?

I was sent a letter from my health care provider about a year ago asking if my my child had any additional insurance. I contacted my ex and was told "no". I reported "no" to my health care provider. I do not want to be held liable to my insurance company or the state for this. What can I do?