Actually, the pics don't tell a very good story :-( Really difficult to see exactly where on the tree the damage occurs. Rather than a head-on shot in strong light, a side view showing where on the tree this happened and how it interacts with the rest of the branch structure would be more helpful. And an early or late day shot is better for clarity than midday.

Until more detail becomes visible, the best I can suggest is make sure you have a clean, cut surface - no ragged edges or torn bark - and no paint or sealer. Just let it be.

But come back with better photos if you can.

That's a very bad wound, it will take many years for the tree to seal it. There is a risk that the tree will never get a good and strong structure again.