Then his level of testosterone can go down.

There's nothing you can do about it. He's not aggressive, he's acting totally normal for a stallion, which is what he believes he is. So, first thing, understand where he's coming from. It's not his fault you didn't pay closer attention to what you were getting.

Second, treat him like a stud, and that means don't put him in with other horses. He will have to be isolated until you can get a vet out to take care of the situation.

Third….get better fencing where he won't get hung up with a shoe or something worse happens to him because the fencing was not stallion-proof.

Fourth, accept that you bought a stallion and get that problem fixed via a vet.