So I have made a similar mistake in my early career, but as others have said, internal promotions can be notorious for this, they are given licence to stick you on the lowest part of a pay band. In some of my roles I was paid more than the lowest part of the next band up.
Experience has taught me that you need to move out to move up. I left a company after ten years and three sideways moves. Since then I have moved jobs twice in three years (one was pandemic related!), and within 3 years I’m earning double and have gone up two rungs of the ladder.
Have a conversation in a few months, if you have no joy then stay for a year, then leave.
And when you leave go with clear, we’ll researched salary expectations. I have interviewed too many women who set their expectation too low, and then immediately get embarrassed and admit they would accept less. Be clear what you will accept (what you are currently on, plus benefits, plus any additional costs, plus suitable uplift). Make sure you know the value of your total package and how much more you would accept to leave.
I’ve done this three times and was successful every time.