Cause left breast redness, dimpling, little 'pinholes' under breast. Nipple no longer gets erect. L breast hotter than R. Good Mammo 2 Mos ago.

Breast symptoms. Unfortunately, a normal or benign mammogram does not exclude cancer with 100% assurity, especially if the breast tissue is dense. If a patient is having NEW unilateral breast symptoms, I would definitely recommend a visit to the doctor and having this checked out.
Need exam. You should be evaluated by a breast surgeon that works in a "breast center", where collaboration amongst different specialties, along with alternative diagnostic techniques are all available in one location. SInce there could be an infection, I would see someone today. Hope this helps!