Issue with bottom of foot after stepping on rock

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Good morning. Two weeks ago I was walking barefoot and stepped on a sharp rock just below the ball of my foot. It didn't break the skin but was extremely painful. I woke up with a very sore lump and a dark red spot in the center. Last weekend I wiped my hand on it and it started bleeding (for the first time).
I went to my Dr and got X-rays showing no foreign substance. He prescribed Augmentin and if that doesn't work is referring me to a Podiatrist. I've attached a pic. It's still very tender and in the morning is difficult to walk on it. Does anyone have any idea what this could be? TIA.