Is It Halachically Permitted to Replace a Wedding Ring?

Hello, I would like to ask about my wedding ring (I think I saw an answer here and that is what prompted me to ask). My ring has been too small for me for several years, and I bought another ring that is very thin and simple, compared with the original ring, which is wide and weighs 9 grams. By the way, it caused me moisture and sores on the finger under the ring. I understood that a wedding ring should not be replaced. But what should I do in my case? Is it permitted to melt it down and make it smaller, or can it only be enlarged? 

Thank you.