Do nothing for a while. Keep them 100% separated for a good month. This will help your boy get used to the new area, and for your girl to calm down and heal from her bite. After this no see, no smell month+, put their pens in the same room. You will have to make sure both pens are secured and that neither bunny can escape. Leave them like this for a month so they can see, smell, and hear one another

After this month+, work on fast short bonding in a neutral room (a small room or pen with towels covering the floor that neither bunny has gone into). Stop all aggression as soon as it happens, and allow mounting for about 10 seconds then remove the top bun, set them next to one another, and pet them for about a minute. Do fast sessions (no more than 5 minutes) multiple times a day in that neutral area, and after a week slowly start increasing the time of bonding during sessions. Only increase time if there is no aggression. If at 10 minutes they fight without fail, end sessions at 5 to 8 minutes instead until they calm down. Once they can handle being in the small neutral space for 5+ hours without any aggression, move to a bigger neutral space and repeat with fast short sessions, slowly increased every few days/a week if they dont fight. Once they are good in the bigger neutral area, start them in a pen in the room they will share, again with fast short sessions multiple times a day, and so on

If you only have a stair gate between them, you need to reinforce it or double up on it, or do whatever it takes to make sure that they can’t nip through the bars. You also have to be aware that some rabbits can jump or climb over barriers. Rabbits can inflict severe bites on noses or other parts of the face, when nipping through bars. You don’t want any injuries, plus, if they fight and nip each other again, that could make them dislike each other and make any future bonding that much harder. If one rabbit did manage to jump or climb over the gate, they would likely get into a fight, with a possibility of severe injuries.

Was Harry just recently neutered at the rescue? It can take a month or more for the hormones to settle down, and some rabbits even go into a post neuter craze, so that definitely is not a good time for rabbits to get together, not even through the bars of a cage or gate.

I assume if they can jump their pens, they will be able to jump the gate so i would not advise it at all. If you manage to get a tall one that neither can jump over, there is still a high possibility they will fight through the bars. I had a fight through cage bars a few weeks ago that caused one of my bunnies to lose skin off of his foot from the fighting. It is very advised you keep your two as far apart as you can for at least a month… You want atleast a month tohelp them forget their dislike for one another and to forget the fighting. While they still have the “i have to fight you” instinct, keeping them close/together will only cause more fights. Some bunnies need a month to forget, others need longer

Cages are the only real safe way to make 100% sure your bunnies can’t get to each other… when sharing a room and you are not there….