I am very sorry to tell you as it is. Your board was damage by the mast. The jagged edge in the gel coat or epoxy coating indicated that the board was not only cracked open but more damage that what you think was done to it. I suggest not to repair anything right now with any epoxy. You need to take it to a professional to have him repair the crack. It might need some fibergalss or carbon mat to be able to help the board support both sides of the damage and make it become one again. It is not a hard fix. Use a pro for the repair and he will be able to make it look like new.