being a chronic disease it cannot be cured in days. A week of steroid
treatment cannot cure the symptoms of sarcoidosis. Sometimes it wont be cured with steroid treatment alone needing more powerful immunosuppressive drugs but sometimes it may be cured spontaneously also, so continue taking the drugs....Since the diagnosis has been confirmed and pulmonary function tests done no need to take lung biopsy
If at all you want, you can see complete blood count
, electrolytes to look for associated comorbidities and liver
function tests to see for liver involvement...