give it a week if the aggression has not slowed some then maybe start thinking of trading the small one in for a smaller one
. i have a pair and they still nip at eachother sometimes. so dont expect it to go away totally but your smaller one should submit in time, that is if it is still a juvenile or a male. i am thinking its a juvenile and fighting to become dominate sex, the female, normal stuff. after it finds out its not the dominate one it will turn into a male..