Jan's decision to stay home from school because she thinks everyone will notice a pimple she has recently discovered on her chin serves as an excellent example of

This is an excellent example of "an imaginary audience".

The imaginary audience alludes to an egocentric state where an individual envisions and trusts that large numbers of individuals are eagerly tuning in to or watching him or her. In spite of the fact that this state is frequently displayed in youth, individuals of all ages may harbor a dream of an imaginary audience.