Welcome to the club. I have drilled through the sides of more horns than I care to remember.
Super glue will work fine. You should have no problems at all. Or, you can give it an authentic repair. Wrap it in leather, with some wire, or sew it. Make it look nice and rustic.
From what I am reading though if you did not find it until you had it in water it is barely there. If it is for you, put some glue in it and TELL NO ONE. If they notice,then they are standing too close. Tell them to back up.
If you are going to make it to sell it, honesty is the best policy. But if it is for your use, use away.
Coryjoe