Yes you need to amend. Did you already file? It should increase your refund and you will get the 1400 3rd Stimulus payment on it!
How to Amend. You should wait until the first return is done processing and you get the first refund.
https://ttlc.intuit.com/community/tax-return/help/how-do-i-amend-my-2021-return/00/2544441
If you were a dependent on a 2020 return but filing independent for 2021 you can get the $1400 now and they don't have to pay it back. So say NO you did not get one because you didn't one, your parents got it.
The 3rd Stimulus payment is really based on 2021. The IRS just sent the checks out using 2020 to get them out fast.
See IRS Topic B first question
Questions and Answers about the Third Economic Impact Payment — Topic B: Eligibility and Calculation...
