It is a citation with no real consequences, except of course the consequence to your wallet. It is a non-moving violation. No one is going to judge you because you have a conviction for expired registration. As long as you renewed you registration within a few days of getting the ticket, the prosecuting attorney will likely take it under consideration and has the authority to dismiss it. Tell them about the one that you already paid. It does not hurt to ask for a dismissal. Good luck.
Legal disclaimer: My answers are only intended as general legal advice based on my experience. They are not intended to be a binding legal opinion nor to create an attorney-client relationship.