Pimple-like things on the cat’s ears may be caused by mosquito bites or bacterial and fungal infections. First, check whether there are parasites and ear mites on the cat. If so, the cat should be dewormed externally, and then Apply fungal ointment to the small pimple and observe it for a few days to see if it improves. If not, you need to take the cat to the pet hospital for examination and treatment.