Is my Macbook m1 air ruined forever?

If the damage doesn't affect functionality, it's a cosmetic flaw only. That means if you can live with the damage ... do so and don't spend the money to "fix" what basically isn't broken.

Be aware, the damage is almost certainly going to seriously reduce the resale or trade-in value.

After deciding whether you can live with the cosmetic damage to the corner, then the main thing is whether the Display is able to fully close or whether that dent is causing the Display to lift a bit on that corner. If the Display no longer fully seats...that is the rubber gasket around the display should be resting on evenly on every portion of the Top Case (aka palmrest and area around the keyboard edges), then it is more likely the Display will become cracked at some point while transporting the laptop.

The picture is too low res and at the wrong angle to determine this, besides it is best to view it in person to see all the details.

We cannot tell you exactly, I suggest that you Contact - Official Apple Support to discuss service options for your MacBook

Best of luck!