You have one year from the date of injury to put your claim in writing to your employer.
I'm getting from the 'tone' of the question that you didn't do that before you left.
IF YOU DID, you have 5 years from the date of injury to pursue 'New & Further Disability' and get medical evidence to show that the back injury produced more disability than originally diagnosed.
If you advised supervisors of the industrial injury (not just 'my back hurts' but actually ' my back was injured by my job, please provide treatment') and you can PROVE you made clear there was a work injury with videotape and memos and emails and reliable witness testimony, you can pursue it ... it might be found that you waited 2.5 years and that's too long, but often unrepresented workers have the Statute of Limitations 'stayed' when they report an injury and the insurer/employer fails to advise them of their rights.
You should talk to a workers' compensation lawyer soon there in your area. Most workers' comp lawyers will give you a free consultation. Call one. You can research lawyers here on AVVO as many lawyers have a profile that will give you good information about the lawyer.
This answer is intended as general information and not as specific legal advice. If you want to have a free consultation with me, please contact me through AVVO.
I agree with Ms. Wallace and Mr. Bollinger. Time to lawyer-up. You may have blown the one year statute of limitations.....but maybe not. Only way to fight this is to get a lawyer who knows W.C.
There are some great WC lawyers in Bakersfield. Find one here at www.avvo.com or at www.caaa.org. CAAA is the association for attorneys here in CA who represent injured workers. Try to get one that is certilfied as a W.C. specialist by the State Bar of California. You can call me for a referral.