Rotten egg smell usually means a 'rich' fuel/air mixture is overloading the catalytic converter, and the exhaust is not completely processed.

It can occur on warm-up, when mixture is intentionally richer, when engine is warm if there is an issue with the fuel management system, or possibly if there is an ignition problem causing a cylinder to 'miss' and dump excess fuel into the exhaust.

Start it and drive it until it is warm, and see if the odor goes away. It might improve with use, if not have a tech check the ingition and fuel systems for proper performance.

Best Regards,
Jim