There are sap feeding beetles that carry oak wilt, and we normally recommend that any injury be sealed as quickly as possible (within minutes) with latex paint or other sealer to prevent disease transmission. After 3-4 days, it no longer matters, because the injury will have dried up enough to no longer be attractive to the beetles. You could carefully remove the loose material that is hanging there, and apply a thin coat of sealer or paint to the exposed wound ONLY if it has been less than 3 days. After that, the sealer is no longer helpful.

The tree will compartmentalize the wound and slowly heal around the edge of the wound. The wound is large enough that it probably will not fully heal over, but that is the most you can really do for it and may live on for a very long time.

This article gives some things to watch for related to oak wilt: https://www.canr.msu.edu/news/leaf-scorch-or-oak-wilt-what-s-plaguing-my-tree