Pink pimples ("neonatal acne") are often caused by exposure in the womb to maternal hormones. No treatment is needed, just time. They can last for weeks or even months on baby's skin.
In the first few months of a baby's life, any rash associated with other symptoms (such as fever, poor feeding, lethargy, cough) needs to be evaluated by a pediatrician as soon as possible. Read more about your newborn's skin and rashes.