My daughter has these as well, and yes sometime, if she will let us, we try to get the white "core" out. But as Tori said, be carefull, clean the area to make sure they don't spread. and just to warn you our doctor said they would last a "few months", it has been 2 YEARS.... we are so tired of these things, but now they are slowly starting to go away one at a time. Just be thankful they are on his tummy, my poor daughter had them on the neck, for everyone to see.
and p.s. if your doctor recomends putting something called "beetle poison" on them to help get rid of them, don't do it. Our ped-dr did & it burned my daughter skin, she was in a lot of pain, got huge blisters that got infected. and it really never got us anywhere, it still took 2 years for them to start going away. Big mess and I wish we would of never done it. oh and one last thing, our doctor also said they wouldn't scar, but some/not all, but some did. I don't know maybe Forty and Fab, is correct if poping them caused them to scar, but some of hers did.