Black screen WITHOUT cursor after Windows 10 installation

I installed Windows 10 yesterday and I had kept my laptop on power and I went away for a bit and when I came back a couple of hours later, my laptop's screen was black but the lights on the laptop blinked so as to show that it had just restarted. So I waited for it to start, however the screen is black and there's absolutely nothing happening.

I googled the problem and found that people could see a cursor or a pointer on their screen but it's not coming for me. Also, my laptop is a 2 year old Dell Inspiron 14z. Can someone help me with this problem please? I need to access my computer, I have to travel in a week. Also, if it helps, I was updating from Windows 8.1 to Windows 10, and I don't have any CD for Windows 8 as it came pre-installed with it, with the shopkeeper telling me that Windows 8 comes installed in the BIOS so there's no CD. Anyway, I really need to access my laptop asap so can someone help me out please? I have got absolutely no clue as to what I should do.

Thanks

That's the thing, the shop I bought it from didn't give me any key, they just said that it's in the BIOS so you don't have to worry about it. They had imported the laptop and it came pre-installed which is maybe why they didn't give it. Also, how do I recover it when nothing is coming on my screen? It's completely black, nothing comes up. I've tried restoring it blindly but it's been to no avail