Thought I Had Medicaid and Didn’t, Is there an Exemption?

I applied last year on healthcare.gov for insurance and listed my adult son as a dependent. They said we would be eligible for Medicaid and they sent our application to the state. I got approved for Medicaid and was covered all year, however apparently my son was supposed to apply to the state separately since he is an adult.

He got approved for Medicaid in September.

Will I owe a penalty. Our income is under 26,000 for 3 people.

Should I not claim him as a dependent on our taxes or do I have to since I put him as one when I filled out the application on healthcare.gov.

He had no income so on his own he would not file taxes and would not owe a penalty.