[Gothmog]

The ring Aragorn wears is the Ring of Barahir, a ring given to Barahir by Finrod after one of the great battles; Dagor Bragollach. It's later used by Beren and was passed on as heirloom among his descendants. So the ring is no ring of power, at least not of that great power.

But I've understood that you've just began reading Silmarillion, right? If so, you can look forward to find the answer to this question of yours. I'm not going to be more specific than this Happy reading, and welcome to the Downs!