Bumps On Groin, Itchy With White Head, Puffy Red, Diagnosed As Infection. Reason?

My four year old son came home one day from daycare with two red bumps on his groin, at the beginning I thought they were mosquito bites, but the following day he started to get more of these bumps all around his genital area, they are itchy and some of them have a white head, other are just really red and puffy. I took him to his pediatrician who told me not to worry because it was just a viral infection, he told me to apply cortisone cream and neosporin if there was broken skin. What kind of viral infection can this be? it his going to go away by itself? It has been two weeks now and I see no improvement.