Elementary OS is hosted on sda5. Win 10 was on sda1(?). I deleted BOTH partitions to resize sda5. I restarted my laptop and was greeted with the GRUB2 interface. I have no clue how to get back into elementary OS.
Wait, you deleted both your Win/eOS partitions? If so, you shouldn't have anything to boot to.... Or do you have any other OS in another partition?
If you still have anything in there, you should be able to run a shell from GRUB2 and list running the 'ls' command (shell> ls) and see what's still there. Then you should be able to edit on of your boot settings to assign the right partition to your boot command.
You might want to grab some references from here