I can almost guarantee you that resetting the SMC and PRAM won't make the problem worse, but then again it is always your choice. Also about the keyboard shortcut, I don't think a keyboard shortcut could change the look of your display but there always is a chance. I looked this up on Google and a lot of results came up with people that seem to be having the same problem as you: https://www.google.com/search?client=safari&rls=en&q=mac+screen+has+black+margin s&ie=UTF-8&oe=UTF-8
I would try one of those.
Hope this helps,
I read through the posts on Google and it seems that re-setting the SMC and PRAM didnt work and I'm really nervous about making things worse. My Macbook Pro is only a few months old, I think I will now go back to the Apple dealer where I bought it and let them sort it out, I assume they will need to take responsibility as it still under warranty? This is my first Mac and I am a bit disappointed that I'm having problems this soon. I do appreciate you've tried to help.