Sometimes coccyx pain can be a sign of an abscess, and that’s a possibility. Do you have a fever or chills? You’re just 12 days post-op, and changes are to be expected, but if you’re experiencing significant worsening at this stage you ought to speak to whoever is covering for your surgeon. In some places that requires an office visit, and in other places a phone call is a possibility. Maybe ask the nurse who is covering for your doctor? In the US you can sometimes more easily get through by calling after hours, since an answering service can contact the doctor who is covering, but they usually don’t contact the nurse.