I'm sorry to hear you lost your Kidney. As far as the pain goes, It is normal since your body has a lack of Redox Signaling Molecules.
The reason you feel pain is because you haven't fully recovered. Children can run and play ALL day, and feel zero pain. In fact, they can jump from bed the next morning with absolutely zero pain from the previous day!
When we're born, we generate 100% of the necessary Redox Signaling Molecules. But when we turn about 12, we begin to make fewer of these molecules. These molecules make our immune systems strong, skinned knees on children heal lightening fast. As adults, if we skin our knee or elbow, it takes twice as long to heal than when we were kids.
Hope you feel better soon.