What Causes A Painful Bump On Tailbone?

hi, iam meena ,past from 2 months my mother going through a sever tailbone pain with a bump on tail bone,which causes pain in both legs,pain on buttock while sitting,cant sleep properlly,always,lying down by back while sleeping, from so many day she did not feel any pain on swelling area,but now a days she find somthing pinching in side the tail bone area.we consultent a ortho.he first refer us for X-rays and said its normal and use hot water with salt and sit on it for a while,but from 2 months no recovery we found...we all r little bit worried...can u plzz tell us some nes tests required and what kind of problem is it and the treatment also. thanx