What will happen if i have nephritis and i skip my prescribed medicines for over a week?

Depends on disease: Nephritis "glomerulonephritis" is different kinds and also depends on the stage of your disease. E.G. If the disease is well controlled will differ than if it was otherwise. Also, missing different medicines have different significance.

Missing meds.: Don't know what medications you would be skipping or very much about your nephritis. I would ask your doctor.