Hello, and welcome to HCM!
There are some basic guidelines that you as a patient can use to determine if a mole or any other kind of skin lesion is concerning for cancer. You can use the memory trick ABCD to remember them.
Asymmetry - skin cancer
tends to have a very asymmetric appearance. If the spot is round or oval in shape it is less concerning.
Borders - skin cancer usually has very irregular borders, whereas benign skin lesions tend to have much more regular borders
Color - skin cancer lesions usually contain different colors, but benign skin lesions typically will be one consistent color throughout
Diameter - The larger a lesion is, the more concerning it is. As a general rule, anything larger that a pencil eraser is concerning and should be looked at by a physician.
Keep in mind that these are general guidelines. Make sure to keep your appointment to have this skin spot looked at.
I wish you well in the future, and thank you for your question.