Small Spot on Spine

I have been having some lower back pain for several months and finally had a CT last month. The CT shows that I have a 4mm Spot on my L2 vertebrae. My onc thinks it might be a bone island, but sent me for a bone scan. The bone scan did not light up for mets, however they say that anything that small will not light up anyway. The spot is too small to biopsy so the onc says "we will keep an eye on it". I am scared witless, as I am constantly reminded that it is there because of the discomfort. It is not excruciating pain, but just uncomfortable. My research on bone islands indicates they are usually benign tumors but my mind tells me, "what are the odds that I would happen to develop a benign bone island during my treatments". I am scared because I know that bone mets are not a good sign.