I was getting ready for my high school reunion and when I looked in the mirror I saw that my entire forehead was covered in pimples right by my hair line.

 Interpretation:

 To see your own reflection in the mirror, suggests that you are pondering thoughts about your inner self. The reflection in the mirror is how you perceive yourself or how you want others to see you. You may be contemplating on strengthening and changing  aspects of your character. 

To see a fine and smooth forehead in your dream, signifies your good judgment and fairness. It is also indicative of your intellectual capacities.

 To dream that you have pimples, relates to issues about your self-esteem and self-image. You are feeling awkward or out of place in some situation or relationship.