Anonymous wrote:I cannot believe how many people are telling you to say nothing! I’m sure you can come up with a kind way to express yourself here.
This! Learn to communicate!
Older married guy here. You are about to get married to this person! If you are not able to communicate this simple but important concept, you still have a lot of work to do, on yourself, and on your relationship.
Try: "I love you and am so happy to be engaged. I love that you bought me this ring and I want to wear it forever. I'm going to bring it in to get a few minor changes made to it so it fits me a bit better and matches my style perfectly. Then I hope I never have to take it off again!"
Or to be honest OP, you can just go do it. I doubt your fiancee would even notice.