The part you are talking about is the brake proportioning valve which is inside the brake master, but you may want to try to smack the brake pedal with your foot to try and toggle the valve back to center which will turn the light off, this light comes on because there is an unbalanced brake pressure, either no brakes in the front or rear. Make sure the brake master is correctly bled here is a video to help:
This guide may help, if not the instructions on how to replace the valve is in the images below:
Here is how the valve works in the diagrams below. Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.
Images (Click to enlarge)
Tuesday, September 6th, 2022 AT 9:01 AM