The rivet on that master link looks very over compressed. The flare on the master link only needs to expand enough to keep it from coming through the bore of the link it passes through. From what it looks like, you may have crushed the "O" ring and the link may be very stiff and compromised. I would get a replacement pin for your chain tool kit and a new master link with "O" rings and redo the master link.
This may be why the pin became damaged. If the pin were too hard a material it could fracture and instead of doing it's swedging, job it would fail.
Ha, I just ordered that same looking kit on Thursday, red case and all. My plan was to grind the rivets off anyway. Just going to use the tool to press on the new master link. $24 free shipping I'll see how it goes and get back with you guys.
Motorcycle ATV Chain Cutter Breaker Riveting Rivet Tool 428 523 530 Cam Drive | eBay
The link isn't tight and it moves as freely as the others. On the installation sheet it gives dimensions of the flaring of the pins (5.4mm to 5.6mm). I measured mine with a digital caliper before and after my attempt. It was 5.4mm and they went to 5.44mm and 5.42mm.