I will echo what Chris said--under no circumstances should you ignore what your doc said in favor of some guys on the internet, but there's a lot of "supplements" that are actually good for the liver/kidneys, or just plain healthy in general---fish oil comes to mind, and it is essentially just a food: you can get fish oil from eating salmon for dinner, just not as much.
So in that sense "fish oil" is actually good for the kidneys/liver, and will not impose any more demands than eating a meal of salmon (actually could impose LESS demands than ingesting whole protein sources).
That is why you need to clarify what he means by "no supplements", up to and including a one-by-one list of individual supplements: omega-3 fish oils--yes/no?, multivitamins--yes/no?, or greens supplements for nutrient support like dried fruit/veggie extracts---yes/no?, or milk thistle for liver health, or supplements meant to help support kidney function and health. Etc. etc.
The other question I have is a big one---Exactly what were your results? Do you have protein in your urine with elevated creatinine, ONLY elevated creatinine but no protein in urine? Do you have type 2 diabetes and/or high blood pressure? Both of those disorders tend to be present (though not 100%) if someone is diagnosed with kidney problems. They also tend to be present BEFORE kidney problems present.
In other words--details, blood work, anything you can say?
As far as workouts, no real need to do a great adjustment as of now, I wouldn't think.