J.L.
Hi A., I would call your pediatrician right away, I looked up this on internet and there has been many people with a black spot on their tongue, for most of them it turned out to be nothing, it can be anything from nothing, to melanoma, to a contatious virus, and sinse I'mj sure he doesn't smoke I would guess a virus, or one lady said heres look like a black marker spot, so has your son got his hands on a black marker? Try not to worry most things with kids turn out to be nothing, let us moms know what you find out if you don't mind. J. L.