How To Treat Sprained Ankle With Persisting Swelling?

i had a sprained ankle and the doctor put it into a walking scotch cast. i noticed there was some dampness in my foot after 11 days even though i was absolutely sure i had not let it get wet. then i felt sore and then couldnt bear it any longer so i used a dagger to saw the cast off. there is what appears to be a fungus sort of a thing near the heel now and i have lots of skin peeling off. i put my foot in hot water tub with salt in it. was that a right thing to do? my snkle is still swollen. what should i do. go to the doctor again or what?