Graphic card. Monitor black screen

Hai, I'm having a problem with my graphic card whenever I try to plug in my monitor on with my graphic card it gives me a black screen. But there is no black screen if I plug it in the motherboard.

The problem occurs when I accidently connected my monitor to the motherboard not the the graphic card. So I decided to switch from the motherboard to graphic card while the PC was running .Yesterday it was working fine with the graphic card but now it is giving me a black screen.How my i resolve this issue.