My son keeps on getting the same pimple on his chest occasionally, what should i do?

It looks like white pus..Its been a while..I haven%26#039;t asked his doctoc because people tell me is nothing..I would like to see if anybody else experience it with their child..|||Does he play sports? If so, maybe his pads rest on his chest where the pimple is. If so, really clean his pads.