I described it as a lump, but after researching some more I realize I should have probably have written swelling. It is like a little patch of swelling, halfway between the elbow and what I can only think of to call the wrist. I think it is swelling on the muscle maybe, as it's on the inside of the leg. I thought maybe an injury from running into her lead would cause this swelling... I'm going to call the vet tomorrow, but I'm going to be researching all night anyway.
Thank you so much