AWS I changed the Master Password for RDS - It messed up my database to server connection

I'm new to AWS as you can tell and I changed the Master Password in RDS and now I'm getting the error:

Unable to connect to your database server using the provided settings.

Filename: /var/www/html/third_party/MX/Loader.php

Line Number: 99

What can I do about this? (I don't know the original password)

Thanks in advance.