Hi, it could be a lot of things, have you hurt it recently? I once put my foot down and snapped a tendon in the ball of my foot, and broke a small bone.
I have diabetes and have noticed if I am not keeping my sugar under control that the ball of my feet will swell. Not sure if you are having that however I would imagine it could add to the pain. Are you having any numbness? It is a good idea (as a diabetic) to check your feet often to make sure you have not damaged any part. My doctor explained that we can hurt ourselves and not know. It is an odd thing to have pain in the foot and numbness as well. Good luck to you
How well controlled is your diabetes?
What is your HBA1C?
Would be hard to know what this is.
What is the quality of the pain? Burning? If so possibly neuropathy. If just aching, maybe arthritis related.