Hi and welcome to the forum! I am glad that I can help you.
You would like to know what can happen in case of stones in the kidneys and nephrostomy.
Nephrostomy is an artificial opening created between the kidney and the skin which allows drainage of urine directly from the upper part of the urinary system. This procedure is done whenever a blockage keeps urine from passing from the kidneys, through the ureter and into the urinary bladder. If kidney stones can't be released from the kidneys down the ureter and urinary bladder, the excess of the urine that is normally produced in the kidney is kept in the kidney and it presses over the kidney tissue causing damage. This condition is called hydronephrosis.
Given the data that you described, you experience nephrostomy. You are at risk of developing kidney infection due to the communication of the kidney with the skin. Increase the level of hygiene in that part of your body to avoid the infection. Consult with a urologist about the maximum period of time during which you can have a nephrostomy.
Please keep in mind that I provide medical information only. I am not able to diagnose medical conditions online. Please contact your doctor or other healthcare provider such as a urologist for further advice and information about diagnosis and treatment options.