i m 25 years old.lest year i fell in a accident. i injured on my back side.then i go a orthopedic doctor.he suggest me some antibiotic medicine. he say me that your injured pleas is blood Coagulate in there.after some days it will out with a Fetid blood.but it does not fully recover. now some infection is out from there.doctor said it is Pilonidal Sinus
If it is diagnosed as colonial sinus it needs excision under local anesthesia, can't be treated conservatively. Try a course of antibiotics if not relieved surgery is the treatment of choice