You should worry about the combination gfr(glomerular filtration rate) of both kidneys. Naturally god has given us 2 kidneys to give us double protection. So even if one
kidney's function is low, other kidney compensates for it. So don't worry. Eventually everything will settle. Be sure to do routine renal tests periodically and don't use over the counter medications or pain killers or native medications that can harm for son's kidneys.
Next Steps
routine renal check up periodically