I have had my current build for two years - ASUS Z270, Intel Core i7 7700K, 16GB of RAM, and GeForce GTX 1060.
I'm getting bored with it and want to upgrade. Can I get a better CPU without changing motherboard?
I know the feeling of getting bored with a build, I change parts a lot myself. With that said, Intel's Z270 chipset pretty much maxes out with the Core i7 7700K CPU that you have.
Not all is lost, though. If you are comfortable with it, you could likely sell your current setup and get enough to purchase a decent AMD X570 motherboard, then you will only be out of pocket on the CPU.
AMD's Ryzen 5 3600 will be comparable to your current 7700K, so you can start there with plenty of upgrade options in your future.