A: Although we cannot make a definitive diagnosis without seeing the dog firsthand, it is possible that there was some external irritant of some sort that started the dog licking the area and the licking itself has caused the progressive rawness and reddening. We sometimes see this with bug bites, a small scratch, allergic reactions to plants and so on.
It can sometimes be a good trick devising something to provide a physical barrier against more licking, but sometimes you can put on a pair of small boxer shorts to help protect the area as it heals. You can also apply some Maximum Strength Lanacane to the irritated area, which contains a topical anesthetic to help numb it and hopefully make him forget about wanting to lick it as much. And/or, you can also apply some hydrocortisone cream to decrease the irritation. With all of these, you have to put on the boxer shorts over it, otherwise he will just lick off the ointment within a few moments. The ointments will not be toxic to your pet, but the ointment once removed will not solve the problem.
Finally, you may give him just a little over-the-counter Benedryl, which may decrease the irritation and make him just a little sleepy, so he will not be as interested in licking. An appropriate dose would be 1 milligram per pound of body weight, twice a day for a few days. If this does not help, then you should make an appointment for us to see your pet as soon as possible. We have other ointments with similar action to hydrocortisone, but in prescription strengths. We can also do testing for allergies and review for other microscopic sources of the irritation.