The 8700K does not come with a cooler. You cannot use it without a cooler.
If you have another stock Intel cooler, it might allow you to boot up without overheating; but I wouldn't try to use it unless you lowered CPU frequency and voltage and disabled turbo boost.
The 8700K does not have a cooler. You need to buy one. YOU WILL destroy that chip if you boot it without cooling. It may "live" but its damaged internally.