[Creeker]

The self tapping bolt itself has cut through and directly connected to the bare steel. That is your ground connection. The star washer helps but is very little of the connection. Its main purpose is to keep the bolt tight.

As long as that self tapping screw is tight and making good contact to bare steel, your good. If you do away with the self tapper then I would recommend sanding the paint away.

My advice; Keep the self tapper or go one size larger self tapper if its loose.