There is a goback option which is available for upto 28 days. You have to get the system to boot into the repair mode, go to troubleshoot and then find the go back option - I have used it once, but don't remember the precise details.
Others may have a better way to get into the repair mode which I find awkward, what I do is start the PC 3 times or so and hard switch off before Windows fully loads, eventually it will boot into the repair mode. I might also learn a btter way of doing this but haven't found it yet.
There is also this which I have just read (and learnt!):
If it’s been less than a month since you upgraded to Windows 10, you can go back to your previous version of Windows by going to Settings > Update & security > Recovery and selecting either Go back to Windows 7 or Go back to Windows 8.1. This won’t affect your personal files, but it will remove any apps that you installed after the upgrade to Windows 10.