Accidently went into reverse trying to go to 4th gear?

1996 honda civic, is this bad? There was a pretty bad grinding noise. Everything works normally though.

A bad grind for a second isn't exactly good for the gearbox but is probably okay. If you actually managed to force the car from third or fifth gear into reverse gear that could destroy the gearbox.

As it's still working it sounds like you were just grinding the gears for a second or so and got away with it. Probably best not to make a habit of it!

OOPS!
Try not to do that too often.