Generally pretty good advice above. The main thing to avoid is straining your voice, and one of the biggest strains is trying to sing outside your natural (comfortable) range. I won't repeat all the good stuff to be found in the thread links above (Alice is an especially good source), but what I would say is, tell the choir director or whoever it is you work with that he or she had better find, hire, draft, or kidnap a good, strong tenor for the tenor section, because you aren't going to sing lead there anymore. Otherwise, the choir might wind up loosing you, too! Not good! And this is not because you're being temperamental—it's a matter of self-preservation.

Give your voice a good rest (a few days at least), then start off easy. Hum a bit. Vocalize a bit. And stay within your easy range. Don't push it. That's what caused the trouble in the first place. And if it still feels uncomfortable, give it a bit more rest. Then, if it still feels uncomfortable or doesn't seem quite right, then get thee to a laryngologist.

Once when I had a bad cold, I made it to my weekend singing job, which consisted of two evenings of singing five forty-minute sets. Then during the week, I gave about a dozen private guitar lessons and taught a half-dozen folk guitar classes (talking all the while). As the next weekend rolled around and I was due for my next pair of five set evenings, I didn't have much voice left. I went to a laryngologist who informed me that I had acute laryngitis. He sprayed my throat with something that made me temporarily unable to make a sound, then told me that if I ever wanted to sing again, I wouldn't utter a peep—not ever a whisper—for a month or six weeks. I should come in once a week so he could see how things were healing up, and then, before I opened my mouth again, go back to my old voice teacher and have him get me started again very gently. I had about two months of no gigs, no lessons, no income.

Don't take a chance on blowing your voice, Nicole. It's not worth it!

Don Firth