When your car says service traction control it means that something is wrong with your traction control on the vehicle and it needs service.
It could be a sensor for the traction control is dirty and needs cleaned up due to road grime or the sensor could be faulty.
It's usually nothing serious but I would recommend stopping by an auto shop and have them take a look at it to be sure it's nothing more serious going on.
Your car has wheel speed sensors that detect when one drive wheel is spinning faster than the other drive wheel and when those sensors go bad or get dirty it can cause problems with the traction control operation.
So it could be just a bad or dirty wheel speed sensor that needs service.