Lump on my dog

Does anyone know what this is it’s on my puppy’s mouth?

Hello!  As with any other lump, a fleshy pink lump on the mouth could be a tumour (malignant or benign) or a cyst.  The nature of the lump in those cases is often down to the type of cell it is made up of, which a vet can get from histology (a sample) if they can't tell grossly.  Sometimes damage / trauma from an opposing tooth, foreign body, a fly bite or even an overgrown area of gum are possibilities, or at a pinch chemical damage eg lip erosions in uraemia.  Your vet will be able to see more than I can and narrow it down, perhaps with reccommendations for tests to narrow it down further.  Im not sure how old your 'puppy' is, but there is a lump called a histiocytoma that comes up in young dogs and can disappear again after a certain time, so depending on this situation, vets may advise that these are left alone for a while to 'wait and see' before they act.  Other lumps, they may want to biopsy sooner rather than later, or try treatment for.   We'd be interested to hear how you get on.