No display on monitor

I tried adding a second monitor to my pc after reading how to do it on google there was a right click go to graphics options I stupidly pressed monitor and got disconnector message and now I can't go. Back (no display) tried vga and dvi leads even tried my tab in case it was resolution still no joy, I work from home so really need my computer any help would be gravely appreciated I've got a matrix logic intel core i3 if that helps