To cure dark circles, the following will help as a part of their effects:
(i) Learn Deep Relaxation Technique (DRT) as well as yoga nidra to deal with dark circles as these may be the result of stress. Regularly practice one of these relaxation techniques to avoid any effects of sleep disorder. Sometimes, sleep disorder is the cause of dark circles. If you do not know about the yoga nidra or drt, you may followup this question/answer for dark circles, so that I can explain here.
(ii) Jala-Neti - Learn this neti. It is very easy but learn only under the guidance of qualified yoga instructor. This is basically irrigating your nasals with saline luke warm water. needless to say that the water should be hygiene.
(iii) Practice Naadhi - Shodhan Pranayama - initially without retention and after few weeks, practice retention in low ratio.
(iv) Do Ushapaan - drink lukewarm water (one or one and a half glass, as per your capacity and season) in the morning upon waking up. Evening should be followed by seasonal fruit juice. Right now if it is winter on your side, you can take carrot juice.
The above may be practiced after consultation with your doctor.