If you have a sore throat and need to sing through it there are a few things you can do. Firstly if you can rest your voice you should, you don’t want to damage it. If you feel that you can sing through or you have a few days to get your vocal chords fit and healthy I would steam 3 times a day for a couple of minutes. My vocal coach says that steam is the only thing that gets down into the chords and it can help the healing process.
Another thing that I do when I feel that a cold is coming is use saline nasal drops. The drops wash out the back of the nose where the cold virus incubates. As soon as you or some one around you starts sneezing use the drops until the sneezing stops. I managed to avoid colds for the whole of last winter by doing this. Although I’ve just had a virus that I couldn’t shake. It works most of the time.