Most importantly, ER docs are in no position to be making judgments about what is or is not a complication of a coblation procedure. I would forget that opinion entirely. If you are concerned about how he has healed after the procedure you should make an appointment to see the ENT surgeon. You should still be within the "global" period for the procedure, so there shouldn't be a charge for the visit. Otherwise, chronic cough has many possible causes (most of which aren't bacterial infections and I am skeptical of the role or antibiotics here).
Thank you for your answer. I agree that my husband should see the surgeon and had told him that actually (the wife is always right :>). I think the antibiotics was because of an inflamation of the nose channels where the procedure was performed but the ER doctor believed the cough was a consequence of the surgery regardless.