Hello. Thank You For Your Time. I Have Rheumatoid Arthritis

Hello. Thank you for your time. I have Rheumatoid Arthritis and I am taking 10 mg Rayos. I was on 20mg for 6 months causing me to gain a ton of weight. I am 45 yes and weigh 218 lbs. I have developed what looks like a bed sore under by belly. (Hangs over my waste) I've talked to my Dr about getting off steroids but he insists they are needed at this point. I have 2 questions. 1. How do I treat this sore? It looks like a skinned knee with a little blood and clear liquid seeping. Very small amount. 2. I go swimming and walking as able. I want to do a crash diet just to lose the weight rapidly then I will maintain a healthy diet. Is this ok? Thanks