I have sle of nephritis, fatigue,severe joint pain butterfly rash,cough,fever,mild swelling,had blood in pee one day could it be kidney damage, flare?

Could be: SLE is a multi-system disease which can effect multiple organ systems. You mentioned that he already had an SLE nephritis. That could cause the hematuria. Have him see his doc soon.

Your autoimmune disease is a systemic disease which may affect multiple organs. The nephritis may be evaluated by a Nephrologist and the urine tested. Adjustments in your medication regimen may be made to keep the disease under control. Watch for abdominal pain, vomiting, fever and weight loss.