Dr. Fitzgerald knew what it was right away (although she did entertain my thought that it was a bug bite after my eyes became the size of pieplates when she said the word "tumor"). The exact diagnosis is Canine Cutaneous Histiocytoma (Wow that sounds scary! For more info, see http://www.veterinarypartner.com/Content.plx?P=A&S=0&C=0&A=1676). Apparently it's pretty common and appears in only a day or two. The tumor is benign & should disappear on it's own, but if she's chewing it or it becomes a problem for her, they want to remove it. Let's hope it goes away soon b/c she does not like the spray I have to apply 2-3 per day.
Poor little toe!