Cucumber cannot cure black circles. There are many ways to get rid of black circles. First you need to know what caused your black circles. If you are lack of sleep and too tired, you need some sleep and relax. It can help the skin beneath. Allergies can be a cause of skin discoloration under the eyes. If this happens, you need to treat your allergies and then your black circle will be cured. You should also keep a healthy and balanced diet, drink enough water and take vitamins every day.
Dear friend, I don't think cucumber can help to solve your problem. While cucumber is good for our skin, we often use cucumber slices as the whitening mask. It really works. You said you haven't sleep well for several days. That's where the problem lies. I think you can have good and enough sleep to get rid of black circles.