I have a bump on the bottom of my foot that causes me a ton of pain, what could it be?

My 3rd toe over on the underneath of my foot I have a bump that causes me enormous amounts of pain. I have had surgery on my ankle/foot to remove cysts and since then my foot an ankle also swell enormously and I am in constant pain. But now this bump on the bottom of my foot makes is extremely painfully to even walk. If feels like every time I take a step I am stepping on a knife or something. Does anyone know what this could be?