Please seek immediate veterinary attention for your gerbil. A vet can properly assess the situation and provide the necessary treatment.
Here are some general tips while you wait for the vet:
* Keep your gerbil calm and quiet. Avoid handling him excessively.
* Provide a safe, warm environment. A soft towel in a small carrier or box can help.
* Do not attempt to clean the ear or apply any medication yourself.
Remember, a vet can diagnose and treat your gerbil's condition more effectively than any advice you might find online. Get professional help as soon as possible.