How do you restore your voice if you strained it?

I got really sick about 6 months ago, and afterwards I realized that I could not hit some of the high notes that I used to. I know that I damaged my voice because I kept clearing it when I was sick and spitting out phlegm and I could feel it getting really sore and raspy. When I wasn't sick anymore I tried to sing and there was one note that I could not hit going up on a scale and also was almost impossible for me to hit any high pitched notes. What happened? What can I do to make it better? I have tried not singing for about two weeks and that did seem to help, but do I need to do it for a longer period of time? I appreciate all of your answers and feedback because I love to sing!