I'm sorry to hear Volt is having skin issues. There can be multiple causes for what you are seeing, including a contact irritation, allergies, an infection (bacterial or fungal), a growth under the skin, or skin parasites. if it is not bothering him, stable, and not growing, you could monitor it. If it is itchy, he is chewing at it or it starts to spread I would recommend he be evaluated by his regular veterinarian to determine the underlying cause for his skin lesion, and start any treatment that he may need (antibiotics, anti-itch medication). Good luck!