I have a large hard swollen painful area on theinstep of my foot only after activity. while running, i can feel it tightening and almost pulsating. what could it be?

Fibroma: You may have a fibroma. These tend to be mor prominent when exercising and can become painful. Try an orthotic in you shoes to compress and support your arch.

Recommend : Podiatric consult. Something's just need to be seen by a doc, this is one of them.

Fibroma: It sounds like you have a fibroma which is muscle pushing thru the plantar fascia or a cyst.