I found this website when I did a search about a lump on my little girl's back and reading it made me feel much more at ease!!!

Jessi is 3 mths old and just had her shots a couple weeks ago and just felt this bump like place on her right back. Going to see Vet in afternoon but was very worried, now it may just be where she got her last shots. You ladies rock. Hope to be around to learn more from you guys!!