Can you see what it looks like? Is it reddish, squishy, like full of fluid? Xena gets those and they come and go. The vet said as long as they pass and don't get bigger or look infected it's ok. Still, if I was you I would bring it up to your vet.
Mr. Eko 2/14/2012 - My first GSD and my little Romeo
Xena 11/30/12 - My first APBT and my little warrior princess