Should i get ct scan for bump on 4th bone of foot that caused pain & swelling? had mri- inflammation. cause of that? my doc-yes, insurance-no.

Yes: It will tell the difference between a fracture and an inflammatory etiology of another cause.

Hard to say: It's hard to say. A foot xray may be able to show presence of fracture or bone formation around the nodule. Not sure if a foot ct would add additional information without knowing the exact findings on mri. Swelling and pain can be from arthritis, infection or trauma. A tumor is possible but less common.