It would be very difficult to comment on the lesions without having a look at them.
From the description you give this could either be - an allergic reaction, petechiae, ecchymosis etc.
Petechiae are tiny, flat, round spots, under the skin, caused due to bleeding.
An allergic reaction could have occurred leading to a rash. Also tight clothing or trauma - accidental due to rubbing etc could have caused the lesion. Ecchymosis is a small hemorrhagic spot in the skin.
Have you noticed any abnormal feature on breast self examination? You should wear lose clothing, keep the area clean. If there is a rash or itching apply calamine lotion and take anti allergic medication.
If the red dots still persist after a few days consult your doctor to get a clinical exmination done.
Hope this helps.