My 15 month old son has a small lump under his skin right above his belly button. My mother-in-law noticed it when, after changing his diaper, she held his hands and he flexed to stand up. Could this be something I need to be concerned about? He has a checkup with his pediatrician on the 25th of this month-should I wait till then? He doesn t seem to be sick or hurting. He has thrown up a couple of times but I was told by the nurse that was because he has drainage down his throat from allergies.