Take your dog to the veterinarian immediately for an examination and diagnosis. Only your veterinarian can determine the exact cause and provide the correct treatment plan. While waiting for treatment, you can use warm water and an appropriate amount of non-irritating detergent to clean the dog's area. Gently wipe the testicular area with a soft cloth to remove any dirt or discharge.
Avoid your dog licking the testicular area to prevent the infection from spreading further. Please follow your veterinarian's recommendations for treatment. This may include oral antibiotics, topical ointments, or surgery.
During the dog's recovery period, the dog's living environment should be kept clean and hygienic, and mattresses and cleaning utensils should be changed regularly. Please remember that the above suggestions are for reference only, please consult your veterinarian as soon as possible for professional advice and treatment options.