swollen paw\pad

seemed to spring up over night is a 10 yr old rat terrier\jack Russell mix from what i believe she was licking her paw all night long. Our thoughts was it could be a spider\bug bite not sure what else this could be any insight would be appreciated ty

Hello!  One of the most common reasons for a presentation like this would be a grass-seed (they are torpedo-shaped at both sharp ends) or a similar small foreign body that cuts into the skin between the toes.  They very rarely present with an obvious entry-hole because often they entered the foot a while ago and can move around once inside;  rather, the first sign tends to be a swelling from when the body reacts to the foreign body and tries to expel it.  Allergies can also present like this, if over-licked and swollen.  Insect or even cat-bites are not completely impossible, but very uncommon.  Usually, when being licked, such lesions are itchy and uncomfortable, so cancer is much less likely than if it were being ignored.  It sounds as though a vet needs to see this toe pretty soon in order to discuss treatments.  I would fully recommend a buster collar, but of course the toe is really itchy (I don't know if you've ever tried not to scratch an itch) so simply preventing licking without treating the toe could be extremely frustrating for its owner.  The top layer of fur and possibly skin looks to be missing, so infection may also be an issue.  Although not obviously life-threatening or anything, this could get rapidly worse if left, so we would advise speaking to your vet surgery today, if only for triage (that is, assessment to see how long it can wait / if anything needs to be done in the meantime).

At home, a warm water foot-bath may help such feet a little, but is unlikely to be sufficient to help an over-licked foot.