Sir or Mam I m 23 years old Mbbs Student..I had productive Cough and mucus congestion in nose  for 8 days 1 week ago and I was continuing antibiotic cepfodoxime proxetil for 10 days due to my Dental molar tooth extraction procedure which was finished yesterday. but no fever at any time .then productive cough resolved gradually but it's started dry cough again while day coughing remains and while coughing very tiny white mucus comes out and tingling sensation in chest and lower throat all time that leads to urge to cough more ...so I decided to do a chest X ray by self but on X ray I am very anxious about the structure I marked or circled on X ray plate ...what Is it is it part of heart or else that whitish circle on left Side close to mediastenum and is the Chest Xray normal?? Sir please provide me the Ans Quick ..