Exercising with Mobility Issue

I'm someone with a mobility issue (fat pad fibrosis of the right heel) which makes it difficult to stand or walk even with my heel taped and in supportive shoes. Running is out of the question and so is any exercise that requires me to be on my feet for a long time. I tried swimming and immediately got a horrible nose bleed and sinus pain and a sore throat and eyes. This has only reinforced my deep fear of pools being kinda gross. I do stationary bike but I have on and off issues with my right knee (I'm doing physio) so I can't bike consistently. I need to have some sort of reliable way to do cardio and to maintain bone density. I'm only 30 and I feel like I'm not able to take care of my body. I'm a little stressed out and wondering if anyone can recommend cardio options? Also happy to receive strength options too (though this one is a bit easier because I could always join a gym with machines that don't require standing). I used to be strong and have great cardio and I don't want to give up!

Any help and encouragement would be super appreciated!