Thanks for the question.

I fear that there is nothing that can be done to save this tree. The damage is too severe. Moreover, the exposed center of the tree shows significant rot. That is probably why the branch broke off. Applying any type of paint or covering to a wound this large would not achieve anything. I would suggest that you obtain the services of a professional, licensed arborist to make an on-site assessment and inspection. See:

https://extension.umn.edu/planting-and-growing-guides/how-hire-tree-care-professional

Sorry to be the bearer of bad news. Thank you for using this forum.