A 32 year-old woman has a pigmented lesion excised from her left calf. The histopathological diagnosis is melanoma in situ, which is completely excised with a- 1 cm margin. What is the next most appropriate management.?

A 4-years old boy presents to the Emergency Department with a two-day history of fever, difficulty walking and is unable to weight bear on the right leg. He has been on oral Amoxycillin 250 mg three times a day for a chest infection over the last five days. He is irritable with a temperature of 39.4°C. He does not allow examination and keeps his right hip flexed and adducted. Blood tests are, (WBC) 18.3 (CRP) 146, haemoglobin 11.3 g/dL. What is the most likely diagnosis?