If you are eligible to be claimed as a dependent, you are legally obligated to check that box and you are denied the stimulus payment under law, even if the person who is eligible to claim you as a dependent does not actually claim you.
If you were not eligible to be claimed as a dependent in 2019 and you checked the box by mistake, it did not affect any other part of your tax return except your eligibility for the stimulus payment. At this time, it is simply too late to file an amended return and it would be a waste of time. You should receive the payment when you file your 2020 return.
if you are still eligible to be claimed as a dependent, then you are not entitled to a stimulus payment. Claiming a payment would be tax fraud, and if you don’t like the rules, you have to take it up with Congress.
