If it’s before January 16, 2024 you should return to the Marketplace as soon as possible, review and update your account information, and shop for a plan that better suits your financial and medical needs. Open enrollment runs from November 1, 2023 to January 16, 2024 in most states, and the deadline for coverage effective January 1 is December 15. Even if your state has a longer open enrollment period, generally you must make your plan change before December 15 to receive coverage effective January 1, 2024.
If open enrollment has ended, you will have to wait to enroll in another plan until the next open enrollment period unless you qualify for a special enrollment period, which you may be eligible for if you experience life changes such as a change in income that makes you newly eligible for financial assistance or a permanent move.
(45 C.F.R. § 155.335).