I Had A Surgery For Stone Removal From My Left

I had a surgery for stone removal from my left ureter through left urs and dj stenting. After the stent is removed the ct scan report reveals "mild distention of pelvicalyceal system and upper 2/3 rd of left ureter noted".I am experiencing some pain which is similar to a nerve pull on my lower back soewhere near the kidney.What is the issue and how can this be cured ?