You are seeing a 4-year-old boy in a primary care setting who has presented with a rash that has been present for 4 days. On examination you note the presence of numerous thin walled vesicles which are golden and crusty. These vesicles are present in the peri-oral and per-nasal areas bilaterally and are present nowhere else on the patient’s body. The patient’s observations are all within normal limits. What is the most likely diagnosis?