Even if you "know" what is going on, there should always be a differential. Especially as a student. There's always that not rare case of what appears to be bronchiolitis but turns out to be pneumonia, or the rare case that turns out to be heart disease. For rashes, there's always a few different things it could possibly be, in order from most to less likely. As a student, you always want to say, the most likely cause is "X" because of reasons "A, B and C, though reasons D, E go against it", less likely it could be "Y" because of reasons "DE, but reasons A,C,D go against it", etc. My plan would be to "obtain lab x and based on that do x, or begin treatment xyz for presumed X and if unsuccessful then try abc".
No one likes someone who appears bored by what they do. Clinic may appear not challenging because people aren't constantly being intubated or on ECMO, but that doesn't mean that you should be foregoing a differential or your critical thinking skills.