Since the hinge is installed in a completed elevator assembly, about the only move you have left would be to push a straight pin into the hinge opening in a few places alongside the hinge pin and inject as much foam safe thin CA as you can get in there. Don't go crazy and poke so many holes to enlarge the hole the hinge pin is in. That will defeat the purpose. Be sure to use oil or vaseline to prevent the entry of CA into the hinge joint. A shot of CA accelerator would help with a bit of expansion.

Since the elevator is secure now, all that's needed is to prevent movement of the hinge that would continue to loosen the part. It should be more than secure enough after the application of CA to fly the plane with no worry. As with all aircraft, a regular pre-flight of the aircraft should be performed before the first flight of each day to assure the airworthiness of the plane, with checks of any important flight surface prior to each flight of every day.

Pat