I Fell On Concrete On The 18th October. Hurt Chin

I fell on concrete on the 18th October. Hurt chin ribs both hands and knee. I didnt pass out orbreak bones (i dont tjink) All better now except knee. I can walk and doesn't give pain when still. Hurts going down stairs or if I try to walk quickly. Can it reeally takes this long to heal? Noiw I am improving I would like to go back to gym. What is the best exercises. I'm am female 66 years old fit and healthy!