Is it negligence from dr if there is screw hitting my nerve after scoliosis surgery &dr didn't consider taking mri till after 49 days of severe pain ?

Not necessarily: Scoliosis surgery is typically complicated, lengthy surgery, and because of that there can be a number of causes for postop severe pain, such as postsurgical nerve irritation/inflammation, pain from the hardware, etc It would be reasonable to consider a postop CT to evaluate hardware placement for someone with severe persistent pain after spine surgery, but this depends on each individual scenario

No one can answer: No one on this site could fairly answer that question without a lot more information about the case and hearing both sides of the "story". Many, many items go into determining negligent care, and this type of forum is not the place to be determining quality of care from other doctors, as we don't get anywhere near all the information needed to make an intelligent evaluation.