Hi what could this be please

Hello!  I'm afraid I'm not sure from these pictures.   I assume that if that was an oddly positioned lump of chewing gum, it would be relatively obvious in the flesh (I don't say this glibly - we vets have all seen such things!)  Assuming that the black is, in fact, keratinised tissue (eg pad), then I would be trying to work out whether it was neoplasia (cancer), metaplasia (change of tissue type in one place), or a difference / developmental change the pup was born with.  Your vet may require a biopsy to work it out.  I hope that that helps a bit!