can i be fired for protecting my nursing license

In Illinois, anyone can be fired for any reason, or for no reason at all;  that's the basic rule.  It's the other side of the coin from your own right to quit for any reason or for no reason at all.  The only exceptions are 1. if you have an employment contract - either as a union member or a personal contract, or 2. if you were fired for some illegal reason like racial or disability discrimination, sexual harassment or retaliation for a previous claim. You might be able to show that your firing was in retaliation for the claim you made, but you will need to prove that with witnesses or some sort of documentation.  The employer will find some error you made, however minor, and argue that that's why they fired you.  It's a tough case to win, even if you are entitled to win. But if it's a discrimination issue, meaning retaliation for the previous claim, you will need to go back to the EEOC/IDHS and file a new claim, and do it soon.  There's a short limit of time.