I would put a call in to your surgeon. Not that I believe there is a problem, but they are there to ease your mind. My mom had her breast removed in 2003 and she has a small knot at the tip of her scar. Depending on how small the lump you had removed was, this could be the same size. Call your doc, I know they are usually more than happy to help. Good luck to you.
Dear Vanessa: A collection of fluid (seroma) or blood (hematoma) is a potential complication of any trauma (such as surgery) to the breast. Depending on the situation, these may need to be aspirated (fluid removed). However, they will resolve on their own over time - but it can take a long time - usually months. Our recommendation is to discuss this with your surgeon who can make the best recommendations considering your situation.