Suggest Treatment For An Infection In The Ear

my son is 3.5 years old .and 2 back befor he compled about ear pain and within a day his ear was becoming red and it swelled, and he is having one little pearsing kind of birth mark so little pus was come out from that particular point,than next day we went to doctor, she cheked and taken the pus semple and given antibiotic and one cream to apply,the report says ther is no infection but after two weeks swelling and rednes has come down but a red pech with swelling is still there and i think pus is also there in that particular pach.can you tell me what it can be and why this pus is coming from that particular (pearsing)birth mark? and this all problem is on the ear nothing is in side.