Spoilers - of course! So if you haven't finished, read no further.
Yes, the problem of the little boy seems to be interesting.
Remember, when the officer asked Ralph if anyone had died - Ralph said that two (Piggy and Simon most probably) - notice that he didn't actually say anything about the little boy; he forgot. Perhaps it is meant that the little boy is so small, so unnoticable that the big ones do not even notice his death - it seems a bit symbolic to Us - couldn't it be compared to a state where the death of some "little person" isn't actually noticed.
The mark seems a bit grotesque to us. Like - it was a detail that helped us remember a member of the mass. Maybe some other little boys perished in the fire but only his death was noticed for he said he saw the snake and had the mark on his face.