Is Vitamin K injection site swelling normal?

My Great Dane puppy accidentally ingested rat poison. I took her to the vet this morning. She was given a vitamin K injection in three places as well as vitamin K pills to take for the next 2 weeks. The injection site on her back has swelled up. I was concerned so I called the vet and was told to put a warm compress on it, watch it and if it gets larger or doesn't go away by tomorrow to bring her in. I'm not sure if I am obsessing over this out of concern. Has anyone else EXPERIENCED this?