Why is there yellow pus from my dog’s penis?

Yellow pus from the penis may be a bacterial or fungal infection from injury. Clean with saline, rinse with metronidazole solution, apply neomycin/erythromycin ointment, then give pet cephalosporins or norfloxacin orally. Use an Elizabethan collar so it doesn't lick the medicine and get poisoned. Keep the home clean and the bed disinfected to cut bacteria.