I just noticed I have a lump on my lower middle section of my back, right on top of my spinal bone. There is no bleeding center or anything... it's just a small lump. No pain, but a tad bit sensitive than other areas. Should I be worried?

Without being able to examine the lump it is hard for us to say. If you haven't visited your doctor it might be time to do so.

Probably nothing, the lump went away after 1 day.