Not Nordstrom, but a related story...
Back when I was losing a lot of weight, I didn't have a lot of clothes on hand, and I was in a Lane Bryant store wanting to replace a pair of jeans. The pair I had on were Lane Bryant jeans, but they'd shrunk so badly at the hems after only two washes, and I'd followed the cleaning instructions on the inside tag. I was looking around, thinking, "Maybe I should buy the long/tall" pants if I can find them. The SA asked if I needed help, and when I explained that the jeans had shrunk dramatically - she replaced them, on the spot at no charge to me. Back then, I did the great majority of my shopping at Lane Bryant because I was still in plus sizes, their service was good, their prices very reasonable for someone needing new clothes every few weeks. I was always so impressed that they instantly replaced those jeans for me, without my even asking.
I'm out of their sizes, but will still shop there for gifts (Mom) and accessories (me).
I strongly suspect Nordstrom would want to make the situation better somehow - either repairing the blouse, replacing it or issuing you a refund/store credit of some kind. If they can make you feel better about this, you'll keep shopping there and won't hesitate to buy things in the future. So, yes - I'd put the blouse into a bag and go visit their customer service counter. It can't hurt to ask, and you're not doing anything wrong by asking.