Noticed a bite on my pups paw

Two days ago I took my pup out for a walk and I noticed she was walking kind of slow. Halfway through the walk she stopped and wouldn’t walk anymore. No noticeable limping up until this point. I carried her home for 30min. She is 14lbs, 10yrs pincher/daschund mix, very chill personality. I noticed she was warm, I gave her some thing for pain (she has torn ligaments in the knee) and she slept. She has been super cuddly and close to me since, but otherwise normal behavior. No excessive licking. I’ve noticed she has wanted shorter walks. Yesterday on our walk I noticed her paw/finger was swollen. I washed it with soap, place saline on it and lightly bandaged it up. When I placed the salt water it started to bleed a bit. The area is pink and very swollen now, definitely deep and I can see the darker spider bite marks. I have her an antihistamine and anti inflammatory, she seems comfortable. I’m wondering if I should take her into the vet or keep treating it at home. I’m a nurse and have some supplies at home. Any help would be greatly appreciated!

Hello  and thankyou for those helpful pictures. Where i am in the UK, a spider bite would rarely make the differentials list for this; I'd be thinking more of a foreign body, a lick granuloma secondary to allergy or pain or an inflammatory reaction around a demodex mite, for example. However, if spider bites are amongst the likely differentials where you are then that may make the list too.  Your vet will help you to create a list according to your dogs' own speficic circunstances and hopefully then you can identify possible treatments together, or else your vet may well organise tests.   I hope that you can together get to the bottom of this conditionn

Interdigital cysts, often secondary to changes in weightbearing of the foorlimb, or even cancers, are strong possibilities here.