I would get a second opinion and get it checked out... It's ALWAYS better to be safe than sorry...
The whole 'dermatologist would be annoyed at this point' is pretty darn stupid... You (or your insurance) PAYS for the service, so it's really not up to them whether it's "worth" looking at or not...
I don't know of a single COMPETENT dermatologist who would be annoyed with getting a mole checked out, whether you have a reason or not. I think your pediatrician is being lazy, and I would find a new one. Any doctor who would ignore something that has been going on for a few MONTHS now isn't one I would want to be seeing any more...
Although, I will say this... My little sister had a mole on her back, that she scratched up when she slid down the door. (Trying to sit down with the door supporting her back...) It caught on something, or maybe the friction of her shirt caused it... There were no other marks on her back, but that mole sure got freaky for a while, and it did grow back bigger than it's original size. She never had any issues with it.
I still say to get it checked out though... like I said, better safe than sorry. :)