Wisdom tooth removed leaves hole. how does it close up?

Tissue Migration: The gum tissue in the area migrates and grows to cover the exposed internal tissues. The gingiva is genetically programmed to do that, just like your skin does.

Healing: A clot forms which starts the healing process. The surrounding gum tissue grows and covers the top of the socket as the surrounding bone does the same below it. Your body is programmed to heal itself. Isn't that amazing?