strange click at end of lever pull after new shimano disc install

[Swiss Roll]

I have 2019 shimano xt brakes, just installed a new icetec rotor, and when i pull hard on the lever, all the way, it clicks at the extreme pull, and the lever moves a lot more in to the bar.
the brakes seem to be ok, i just tried to avoid this click on the way to work today. it's the back brake, by the way.
Anyone got a clue what this might be?

 

[RustyIron]

Summary of your problems:
1. Clicking noise.
2. Excessive lever travel.

When you have multiple problems, start with the one that you understand and can easily resolve. By the time you fix the first problem, you might automatically fix the second, or at least have a better understanding of what's wrong.

Problem #2 is the obvious place to start. Bleed your brakes, completely replacing the old fluid. Do that, getting the brakes operating perfectly. Then we can talk about any unexpected noises.