3 things that you must carry with you while driving: valid insurance (pink card) with T/P liability coverage (pay in case you hit a Third Party, bylaw at least 200 K). Valid registration (this is the proof of ownership, prove you own the vehile, not stole). valid driver's license. missing of any of the three will result a ticket, (first time driving with no insurance is penalty, second time is go jail), your car is towed, and you have to pay for towing!
Go to the registry right now. and go to court, tell them you forget to pay it and show them that you have paid already. Most likely you don't need to pay anthing.