I agree with others that you should take the pics to your ped and let her know that you aren't comfortable with no knowing, and that you want more info. She didn't know that it might have been there before, and looking at the pictures might change her opinion. She needs all the information to give you good advice, so don't feel awkward about making another appointment to discuss it again now that you have more info.
That said, my older fell down steps when he was 17 months old (so scary). He is 12 now, and we can still see the lump on his forehead. A stranger wouldn't notice it if no one pointed it out but I can see it easily. It's the scar tissue from the fall, and he'll have it forever. I don't know if this is what you are seeing. Maybe it is something different if it was there before the fall. I don't know, but your ped can help you sort it out.