Best weight loss exercise for someone with an injury?

I want to lose some weight, but I can’t do anything very strenuous because of a rib injury that won’t heal, so what are my options for losing weight? Is just walking my best bet? I’d like to be able to do something else from home (don’t currently have a treadmill) because it’s extremely rainy now.

Additionally, I’d like to lose some weight by February/March, so what’s the most I should lose by then, so that it won’t come back?