Welcome to healthcare magic
What you are having could be truncal acne
. Acne or pimples
can occur not just over the face , it can also occur over chest, shoulders and back.
I recommend you to see a dermatologist
and it can be controlled by medications.
You may apply a cream containing Benzoyl peroxide
5 % at night over the area. I am not sure whether you get this over the counter in US. Avoid applying greasy creams over the area.
Hope this helped