Are Antibiotics Sufficient After Surgery Performed On Infected Sac In Ear?

my son was born with a pinhole on his external left ear. Few months back pus has been forming and were advised for surgery whereby the doctor said that he would take out all the infected sac in the pinhole area right from the root. But after three wks from surgery the stitch wound has been oozing with bloody n pus and the doc has now put him on antibiotic and does not know the cause for its reoccurence.....