Help me with my engagement ring!

So my fiancé proposed to me four days ago and I was actually so surprised!!! We picked out my engagement ring together a few months ago just because I’m so picky, and I fell completely in love! We bought it at a “non” name brand or a not largely known jewelry store in the city we live in but not a pawn shop sketchy place either. I’ve worn it now for only 4 days, and it’s leaving a mark on my finger! I only wear gold, so I know how it reacts to my skin and I’ve never had a reaction to real gold (10k or 14k). I’m looking at the ring, and it doesn’t have a stamp either that says what “k” gold it is! I read online it can be from resizing the ring and smoothing it out the stamp can go away, but I have no idea. It’s a legitimate jewelry store, but I’m so confused! We spent $2000 on it, and I have the appraisal card they gave me that says it’s 10k gold and what carat the little diamonds are. I’m really confused! Should I go to a different jewelry store like a Zales or Kays and see if they can test it and if it’s fake, confront the store?! I don’t know!!! And should I tell my SO? Because he wanted to go to a name brand jewelry store, and I didn’t, so it’s kind of my fault. I don’t know because I’ll feel like he’ll be mad if he finds out! Help!!!