You will have no damage. If you shorted between the positive battery terminal and ground, via your ring, no critical trailer wiring or devices was involved, just the ground cable from battery to the frame. It's just like shorting across the battery. If it was for more than a few seconds you might have damaged the battery.
In my youth I had a battery on my workbench with a battery charger hooked to it. Bumped the cable and the charging clamp twisted down and hit the other battery post. After about 2 seconds the top of the battery blew off. Since then I have always had a cautious respect for the power of a car battery.
There are 10 types of people in the world.
Those that know binary, and those that don't.