Yes you can code the fever that is the main reason for coming to the Dr office, and the history section of the note should state "patient with one day history of fever with taking tylenol" then the Dr should order labs to see if the patient has an infection of some sort usually they will order a CBC to check the white count that will see if they have an infection or viral infection, on how they will treat the fever or let the patient continue on Tylenol.
That is presenting chief compliant of the patient. Yes fever can be coded.