Here's why you should take your cat to the vet immediately:
* Infection: The pimple, pus, and odor strongly suggest an infection. Untreated infections can spread and become more serious.
* Underlying Conditions: Skin issues can sometimes be symptoms of other health problems.
* Proper Diagnosis: A vet can identify the specific type of infection (bacterial, fungal, etc.) and determine the most effective treatment.
Please don't delay in seeking professional veterinary care for your cat.