Hard lump in sub-occipital area, told it's bone. Always sore. Previous MRI & CT of neck showed straightening/reversal of cervical lordosis. Same thing?

Unlikely. Many folks have a prominent bony excrescence "bump" along the inferior midline occipital bone. Straightening of the cervical lordosis can result in the normal posterior spinous process of the vertebra to feel more obvious on palpation but should be lower and easy to differentiate on CT.