Yes, it may be. If you were crying for a long time last night, the circulation around the eyes may be hindered. In addition, the nerve system may be affected. Once the blood circulation around the eyes are stopped or decreased, it appears easily the black eyes. If you want to release this symptom, you'd better use the cold towel to adopt it to make the circulation go on fluently.
Nope, it couldn't cause that in this case. The black eye is described as the bruising around the eye because an injury to the eye. The most common cause is a blow to the eye or nose. However, crying causes blood to rush to the surface of the under eye skin. It can cause your eyes to swollen up and redness, even your face could get puffy. It results in dark under eye circle instead of black eyes.
Of course no, crying too much can just make your eyes red and swell up. There is nothing to do with a black eye. A black eye is most commonly caused by something hitting the eye or nose. Either one or both eyes may be blackened depending on where you get hit. Other types of trauma to the head can cause black eyes, including skull fractures. So you should check out what is the reason, and then have a treatment. For example, you should have a good Rest and put some ice early after the injury. It will help to decrease swelling and pain. Besides, you must protect the area from further injury by avoiding athletic or other possibly injurious activities until the eye has healed.