What shots did she and your other doxie get. I remember this happening to one of my pups my schnoodle I believe after her first Bordatella or it may have been rabies, I can't recall the exact one now. However, I did notice she developed a quarter sized raised knot near the outside shoulder area where she got a shot it was there for a few weeks my BF at the time and I decided to watch it and if it grew or got painful to take her in and have it checked out. It's not uncommon for them to have a little injection site tissue swelling reaction so that may be it but if it worries you or bothers your little one then most definitely take her in!
The fact both your pups have one and they both got shots makes me think that's what it is. Usually if they are just giving a vaccine that can be subcutaneous (under the skin) they just choose a place with a little extra skin and give the injection. It truly depends on the doctor or Vet tech that gave the shot as to the spot they choose.
All in all, my pups swelling went down after about 2 weeks but some can last longer or years if it bothers you or her please don't hesitate to take your little one in