What Causes Hard Lump And Pain At Tailbone?

I have had tailbone pain which is worsening over past four months and now causes deep aching in hips and liwer back vi have a hard lump on tailbone which is growing. It is not visible but can be felt it is groeing more to the left on railbone bi am now getting some numb spells in liw back and a burning pain around railbone for past two weeks. An exray showed something in tailbone which dr says resembled an old fracture. I have never injured my tailbone. I am waiting for an MRI in February but the pain is worse each week. Is this likely a tumour?