Tough to say without seeing the lesion. One consideration would be a neuroma, which is an enlarged nerve, that can cause lumps and bumps in the finger.
You may want to consider imaging the lesion - perhaps with an ultrasound for further evaluation. If it causes discomfort or persistant problems, surgery can be considered to remove the lesion.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Kevin, M.D.
Medical Weblog:
kevinmd_b