I've read that Raspberry GPIO ports can't withstand +5v and works only with +3.3 v, and that +5v could potentially permanently damage the port? But what does it mean exactly? Is that specific channel broken meaning that it can't be used reliably neither as an INPUT nor as an OUTPUT, it works as an output but it doesn't work and input?
The actual answer is it depends.
If you specify in more detail exactly what you intend to connect we can give you a better estimate of the probability that you will destroy the Pi or GPIO, but no one can give a definite answer because this puts the SOC into an indeterminate state. This can cause catastrophic chip failure, a simple GPIO failure, a latch up failure mode which is recoverable on removing power or if current is limited (which effectively prevents the actual voltage exceeding 3.3V + ~0.7V) no impact.
The simple answer is DON'T DO IT