Bad cut in gums

Hello!  That looks sore and as though it ought to be seen; it would be a good idea to get this case triaged by an emergency vet (if the pup's ok, maybe first contact over the phone?)  It's hard to tell on the picture how badly it's bleeding, how the rest of the dog is or whether there's a foreign body in there.  Best of luck and please let us know how you get on!

('Triage' is first contact with a veterinary team where they establish how urgent something is, ie does it need to be seen immediately.  For me it would depend a lot on things that I can't see properly from here.  All the best).