i got laid off and i was told since i was off for work injury the guys they hired after me have been working when i wasnt so i was laid off

Under Illinois law, the company cannot terminate you for having a work related injury.  This would be retaliatory discharge.  If you were back at work when they decided to then lay you off, you may have a strong claim.  If you were still off work when the company laid you off, your case may be a little more complicated but you may still have a legal claim. I highly recommend that you consult an attorney and discuss more details with that attorney.