What Causes A Painless Lump Between Rectum And Vagina?

Hi I have a lump under the skin between the anis and vagina. It's about the size of a golf ball. I had a colonoscopy today and found nothing. I have been told it may be my cervix. I don't understand. It is not painful but I can feel the pressure of it. My sister died of cervical cancer last month so any help is greatly appreciated Thanks.