Bleeding when using metronidazole can be caused by a variety of factors. If the finger goes too deep into the vagina, it may irritate the cervix, which may become inflamed or congested, or even eroded, and bleeding may occur because of the irritation, so it is important to observe the medication for as long as possible. When there is inflammation of the vagina, bleeding may also occur due to irritation from the medication. Regardless of the type of bleeding, it is important to stop the medication if possible and wait until it has cleared up completely. If there is bleeding again, you should go to the hospital for a checkup to rule out the possibility of ruptured blood vessels or cracks in the vaginal wall to avoid affecting your health.