Cat bit my hamster's ear, I see dry blood. What should I do now?

Thank you for using Petco Pet Education Center, formerly Petcoach, sorry to hear that your hamster was bitten! If the area is no longer bleeding and your hamster has a normal level of activity, and is eating/drinking/urinating/defecating normally, you can continue to monitor for any signs of infection (discharge, swelling, or redness). If you notice these signs, you should have him evaluated by a veterinarian as soon as possible. In the meantime, you can carefully trim your hamster's nails so that he does not traumatize the area while grooming and apply a very small amount (just the tip of a Q-tip) of silver sulfadiazene (SSD) or triple antibiotic ointment such as Neosporin to the area. In the future, I recommend not allowing your cat near the hamster cage, or having a very sturdy lid to avoid accidents.