I wouldn't take that to mean anything in and of itself. You need further investigation/identification, is the bottom line.My cats lump is hard too.
My cat's tumors are located in completely different regions of his body (head/neck/chest) and the pathology report said the particular tumors that were biopsied possibly originated from regional lymph nodes, but that particular aspect is inconclusive. Although the disease is 100% confirmed as large-cell lymphoma.
I am just trying to describe the details of my cat's case, but the fact that the lump you are dealing with is on her paw, it's likely a very different cause. And could very well not be cancer.
I don't know much, but I do know I'd pursue further steps to get the problem identified, as soon as you can. Other wiser users can chime in with advice on if/what the hardness of the lump could mean.