My dog seems bitten by another dog; its penis is red, swollen, bleeding, and a bit pusy

A dog’s genitals bitten usually involve bilateral purulent infection, possibly with torn cavities; promptly take it for sterile debridement at a clinic. If a visit is inconvenient, first sedate the dog, shave the fur around the wound, flush with hydrogen peroxide or saline, and wipe the pus with gauze.

After cleaning, disinfect with povidone-iodine and apply antibiotic ointment (erythromycin) or Chuanglide spray (Puante), and give oral antibiotics (Aisuda) to prevent secondary infection until the wound heals. Fit an Elizabethan collar to stop licking.