Midnight lycanroc are rather difficult to handle, so I admit I’m not entirely surprised that yours is having difficulties adjusting. This is, of course, compounded by the fact that midnight lycanroc are often eager for battle, so to be placed in a situation where he isn’t fighting as often as he normally does means he’s bottling up energy due to a lack of constructive outlets for it, rather than releasing it on the battlefield the way he would naturally.
That having been said, the best thing you can do for your lycanroc is to provide him with an alternative means of releasing that energy. This may be as simple as setting up a training area with a training dummy (have a friend assist in the construction of such a space) where he may practice his moves on inanimate objects while you observe. Alternatively, you may wish to call on a friend to battle against your lycanroc daily or to take him out for battles while you recover.
Granted, the former may require some physical exertion on your part, and the latter doesn’t entirely build trust. These are simply straightforward answers to lycanroc’s predicament, but there is a third alternative: channeling his energy into another activity. For example, some dog pokémon trainers teach their partners ordinary dog tricks to help them bond and to hone their focus on a particular task. Some trainers simply take long, easy walks through scenic parks or along trails. And some—particularly the owners of dog-like pokémon that are also humanoid in nature (midnight lycanroc being one example, with the likes of lucario and zoroark being others)—teach their pokémon more complicated skills such as painting, playing instruments, yoga, or even cooking. Perhaps allowing your lycanroc to do more about the house would also be an effective outlet.
Ultimately, be creative but also try to see what interests him the most (besides battling). Communicate with him as much as you can and give him options. And above all else, promise him that you’ll battle alongside him eventually, but your own physical limitations prevent you from doing so right now. You’ll be surprised by how easily he’ll understand that point, even if he’s naturally eager to battle.
Best of luck, anonymous, and get well soon!