The muzzle threads are very thin and will bend, especially with the leverage of an ldc. You can chance bending it back (may break) or you can shim up the back of the scope rail.
Sorry to hear about that . Is the barrel visibly bent ? If it is not the scope could be the issue . If you had it sighted back in after dropping it and then picked it back up next day and it was very low and would not adjust lower I'd suspect a scope issue . I'd suggest trying a different scope or trying the scope on another rifle . Could also be an issue with the ldc . have you shot it without it to see if poi was still very low ?If the barrel breaks at the threads the barrel would need to be replaced . It is the barrel that is threaded .