How do I repair a 4in dia.&6 in.deep hole&12 ft from the grnd. on my living narra tree,due to rot and insects?

i cut a branch 2 years ago on my pet tree and the cut has been infected by boring insects and whenever it rains, which is a lot in Manila, water enters the hole and is rotting away the inside of my narra tree(our national tree in Phil., hard tree like Mahogany).pls. help I love this tree, it gives cool shades during the hot summer months .