feeling a step or a lump in the spine is a "must see doctor "thing. it seems that you have consulted one and he has advised a MRI
of the spine. you should also ask your doctor to get a x ray
or CT scan
of your spine as it will tell about the bony alignment of your spine much better than MRI, as your case may be. till than get absolute bed rest
, can wear a corset also. take pain killers SOS and limit your activity .