Urine report shows protein 15mg/dl, rbc =occasional, serum creatinine increase to 0.81mg/dl from 0.76 in a month. mild left flank pain. what is this?

Just watch & see...: Your one-time reported difference in urine & blood laboratory findings should not incite worry, just just watch, wait, see, & repeat them in 3 months as needed depending clinical profile may evolve. And if pain in left flank is really from left kidney remains to be seen, but detailed history + physical exam + timely imaging studies such as CT scan or US will help define the myth behind concerns.