Poor Diesel! Thank you for providing a picture of his wound, it helps me formulate my answer. It looks like it may be starting to heal, I think I see a scab formation starting, and I will give you some advice for general wound care at home. I would gently clean the wound with warm water and antiseptic soap. To keep him from licking at it, you can put an Ecollar on him. You can get one at a pet store or make one at home. Keep the wound clean and dry, and monitor it for signs of infection. If you see redness, swelling, warmth to the touch, or pus, then it is infected and he will need to see the vet for antibiotics to treat it. Hopefully it heals without problem!