Very top left of my spine feels bruised to touch what could cause this?

Spinal pain: Likely sprain or strain. Consider overuse.

Varies : Assuming that you did not actually bruise it, there are a number of spinal conditions that can pain and a local hypersensitivity. Examples include a pinched nerve, a paraspinal muscle spasm, and a referred pain from a degenerative facet joint among other possibilities. I would not hesitate to be seen. A detailed exam and appropriate studies would likely show the cause.