Hi. Acne vulgaris commonly occurs on the face, chest and back. Although it is possible for the odd pimple to grow anywhere, this sounds more like a follicular conditon. He should see his doctor for a definite diagnosis and treatment, probably with a medicated foam.
Popping any type of spot should be avoided. This seldom improves the appearance and will spread bacteria under the skin leading to future breakouts. Squeezing spots can also lead to a secondary infection, making diagnosis more difficult.