Based upon what you have at the top of the differentials how would you treat this patient?

Johnny is a 5-year-old Asian boy who is brought to a family practice office with a “runny” nose that started about 1 week ago but has not resolved. He has been blowing his nose quite frequently and “sores” have developed around his nose. His mother states, “The sores started as ‘big blisters’ that rupture; sometimes, a scab forms with a crust that looks like “dried maple syrup” but continues to seep and drain.” She is worried because the lesions are now also on his forearm. Johnny’s past medical and family histories are normal. He has been febrile but is otherwise asymptomatic. The physical examination was unremarkable except for moderate, purulent rhinorrhea and 0.5- to 1-cm diameter weeping lesions around the nose and mouth and on the radial surface of the right forearm. There is no regional lymphadenopathy.
Write a differential of at least three (3) possible diagnoses and explain how each may be a possible answer to the clinical presentation above. Remember, to list the differential in the order of most likely to less likely.
Based upon what you have at the top of the differentials how would you treat this patient?
When would you allow the student back to school? Elaborate on your reasoning?