Spot on bottom of foot. Very painful. Dr says not planters wart. Turned purple with spots under it. What could it be?

See below. It could be a vacular lesion or ganglion, or fibroma.\ should be removed and biopsy done.
See a dermatologist. It is difficult to make a proper diagnosis since I am not there to see the condition. I recommend seeing a dermatologist so that they can make a proper diagnosis and give you something to get rid of the condition or relieve symptoms.