Short Term health insurance is not considered minimum essential coverage under the ACA however if you’re uncovered only 1 or 2 months, you don’t have to pay the fee for any month. See HealthCare.gov
Here's how you would enter that you had short-term health insurance for one month and 1095-C Employer-Provided Health Insurance for 11 months:
Related information:
I didn’t see this until after I submitted. Will it all work out?
Did you answer that you had health insurance coverage all year? Since the fact that you did not have ACA compliant insurance for 1 month did not affect your bottom line, you won't need to amend. It should be ok.