We don't see any clear indications in the photos that a borer is responsible for the symptoms, though not all areas are well-lit or in focus. Other potential causes of sunken bark areas and oozing sap (termed "gummosis") include physical injury from wildlife or gardening equipment or canker infections (which often set in after plant stress or damage).

Nothing can be done to remedy the wound; it will seal-over on its own in time if it is capable of doing so; don't coat or spray it with anything. No pesticide will kill wood-boring insects once they are inside the wood, and any preventative measures taken to discourage future generations of a borer from entering the wood again would first require identification of the insect species responsible. (This is because their life cycles differ, and so would the timing of any pesticides used. Such pesticides are not selective, though, and would potentially harm any insect, beneficial or otherwise, that comes into contact with spray residues. Given that, we rarely recommend them for home garden settings.)

Borers and some pathogens tend to target trees/shrubs under stress (even if no other symptoms of that stress are evident yet), which can include drought and root damage. The best approach for now is to keep the tree's roots in good health by continuing to monitor it for watering needs as this worsening drought continues.

Miri