When ticks attach themselves to their host (our pets!) while they are sucking blood they release a bit of fluid- that makes this little knot about the size of a pea. My vet said not to worry and that it will go away. I remember my other dog had a tick years ago and after we removed it that little knot was there for months...dont' be alarmed. As long as you get it removed and clean it, it shoudl be ok.Keep me posted.