1) Call down to the place where you pay your tickets. Varies by municipality.
2) Inform them that you were given a repair order for a headlight or something else, tell them it was fixed and ask what you have to do now.
3) Assuming they don't ask your name or anything to check on it, they will probably say "Oh, as long as you fixed it you're fine."
4) Casually ask "So there's nothing I have to sign... nothing or record or anything, just 'that's it'?"
Call from a public phone somewhere and just hang up if they ask for your info. 😛