I noticed it a couple months ago maybe 2/4

My sons chest is always clear but I noticed he had like a pimple like wart or cyst under his nipple **just one** then a few weeks later another one appeared.. & now I just noticed another small one on his rib cage. I know it’s not a pimple but it looks like it based on how raised it is but it’s white? Anyone know what it is? & how it can be treated?? He said it don’t itch or anything .. thank you