This may be a common wart or a ganglion cyst. I advise that you see a dermatologist about this problem for accurate diagnosis and treatment. If this is a wart then the dermatologist can try to freeze it off which takes a couple of weeks for results. He/she may shave the area down also. If it is a ganglion cyst that has protruded so much that it is very noticable on the finger then the doctor may take a biopsy of it or extract any fluid with a small needle. I have added some links for more detailed information on ganglion cysts:
Ganglion cysts - DynoMed.comeOrthopodIf this answer is helpful please click the accept button. Thank you.
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