If your income is low enough, you should not have to worry about paying it back. However, since I don't know your entire tax situation, I can't say that for a fact.
If you received a subsidy (Advanced Premium Tax Credit) for health insurance through a marketplace, such as Covered California, you will have to file a tax return regardless of your income amount and source. You will receive a Form 1095-A which will be reported on your income tax return.
To set your mind at ease, please see this link is to CA information about the Premium Tax Credit which discusses some qualifications and which seems to align with the IRS FAQs about the Premium Tax Credit