What is this black dot on my toenail could it be cancer?

Jackie, it's most likely a blood blister that hasn't grown out yet. Blood blisters are bruises which can form under a finger or toe nail in response to some sort of traumatic injury to the area, such as your getting stepped on by something heavy or dropping something on your foot, for example. They normally heal without any treatment, and grow out over time. You don't have cancer, believe me.

Most commonly it is bruising from an old injury you forgot about minutes after it occurred.
There is a tiny possibility this could be melanoma.

its not cancer

Prudent to take it easy and concentrate more on your studies to come out with flying colors.

No. It's you being a drama seeker. You already know you have mental problems so why post questions like this here instead of seeing a doctor if you are honestly concerned.

Could be dry blood under the nail.

I don't think so, it's probably just a bruise