I'd just use some first aid tape, either the cloth or paper kind you can get in the first aid section at the store and stick it on the collarbone where you get sore prior to putting on your gi. It's cheap.

Maybe try and get some stuff like Body glide. Bicyclers use it to stop chaffing and so to do ironmen and surfers to stop wetsuit rubbing. Trust me there is nothing more annoying than a wetsuit rubbing on the back of your neck and irritating it but i use different types of bodyglide like products and it works beautifully

Mine doesn't.

It's been a while since I've dawned a Gi. I broke my collarbone a few years ago and had surgery and everything but now it sticks out noticeably further than my other. I've also noticed that my Gi rubs against it a considerable amount and it gets quite sore after a short time. I was wondering if anyone else has had this issue before and if anyone has any ideas or solutions they could share. thinking I might just wrap my shoulder to relieve some of the pressure