There are hair folicles all over the breast. Or it could be irritated from clothing or your bra rubbing against your skin. Or it could be from sweating, i know that when i work out i sometimes get little pimples there too. My mom had Inflammatory Breast cancer with nodules on the skin and they were huge round welts that were the size of quarters. And they were the last presenting symptom of her cancer, so I wouldn't worry about cancer (easier said then done, I know). And so I'm not creating anymore anxiety, IBC is very rare, around 1% of all breast cancers are IBC. And we are pretty sure the fact that my mom and her sister, who was diagnosed with lung cancer years ago, were given weekly chest X-rays for over a year and a half in the 50s because their father was suspected of having TB was the huge contributing factor to both of their cancers, since no one else in our family has ever had cancer.
I know exactly what you mean about one worry going away and then another pops up. I was just at my doctors again today with swollen lymphnodes in my neck. Was sure it was lymphona, nope. A pretty nasty inner ear infection. So my advice is to put some warm compresses on it, try not to mess with it and then let your body handle it naturally. And if it doesn't go away by next week then see your doctor. Sometimes our bodies need a little help. Take care, and try not to worry