Draco started wearing rings on his fingers in his third year, his fingers adorned in chunky silver jewelry that accentuates his fingers and hand movements. However, you've noticed that he'd keep his ring finger on his left hand completely empty, he'd cover the rest of his fingers with rings, and leave that one empty, drawing your attention to it.

You were relaxing in the common room with Draco while he did his assignments. You played with his left hand as he wrote, ditching his other fingers