In this case, where you have a clear non-uterine cause to which to attribute your bleeding and where you have two years of not having uterine bleeding, your bleeding is considered dam makkah, blood from a wound. (Sometimes cervical polyps toward the inner, more uterine, part of the cervix are treated more stringently, but we would not be stringent with you because you are post-menopausal.)
Dam makkah does not make a woman niddah. You are not required to perform bedikot or to wait seven clean days, and mikveh immersion is not required. So long as your bleeding is consistent with that expected from your cervical polyp, you may attribute it to dam makkah from the polyp.
Once the cervical polyp is removed, any bleeding situation will have to be judged on its own terms. Fibroids can sometimes be associated with bleeding, so you may wish to take that into consideration when deciding what to remove.
Refuah shelemah!