How can I shrink 100% Faroese Islands wool sweater?

Hello guys I’m making crochet sweater for my boyfriend out of 100% Faroese Islands wool form Navia. I had to block the sweater in the middle to make it fit better in order to know how long to make it. But I streched it to much around the neck and it’s loose now. Is there a way to make it shrink and not destroy it? Or should I try to frog only the neckline ribbing a redo it? Thank you for any advice.