this happened to my rear brake pedal a couple of years ago.
there is quite a simple remedy.
you just have to remove the pedal and scrape off all the gunk that has collected. when you remove it, you will see how the gunk has hardened that it actually looks like a spacer. this is not the case, just clean it off, be reasonably gentle and grease/lube it before replacing.
this is part of my annual servicing now, (the only thing I really do myself)
it is not difficult to remove, couple of bolts/screws.