The source of the damage was not the physical skyscraper-tall splinter. If that was the case then digging deep enough would always result in making Azeroth bleed. We have plenty of dungeons and Titan engines that go much deeper.
This should be even more clear that the source was magical in nature, and not physical, as we had to use the power of our artifact weapons to seal the wound by draining the sword of it’s power. The red glow in the weapon disappeared, our artifact weapons acted as vessels for that power (as they had acted as vessels of power throughout the expansion), and we moved on. We didn’t have to remove the actual sword to heal Azeroth. But everyone is losing their minds over the sword itself still being physically present.
TLDR; source of the wound = magic, not because the literal physical sword is sharp and pointy