For ~4 days I had mild r/s flank pain, worse when urinating, w/2 episodes of cloudy urine only. 2 days later, symptoms are almost gone. Do I need Dr.?

Possibly. Symptoms suggest a possible UTI or perhaps a small right sided ureteral stone. Push fluids and if symptoms return or worsen please see your primary care doc and have an exam, your urine checked and possibly a KUB X-ray and a renal ultrasound as needed.