On most Ideapads, especially the slim ultrabook models, there should be a (very small) Novo button right next to the power button on the front:
https://www.manualslib.com/manual/577626/Lenovo-Yoga-11s.html?page=16#manual
This will launch Lenovo's OneKey Recovery program where you can find different boot options. Hopefully, this will solve your problem, but if you're installing Windows 10 this sort of thing can happen, and in some cases you may have to factory reset the machine. That's where you use the Novo button.
Best of luck,
GreyCatz.