I got hurt at work 2 weeks ago but my employer won't let me file through workers comp.

Location: Colorado

I hurt my back at work while doing some heavy lifting at just thought it was a pulled muscle. I let my boss know immediately and he said to let him know if it didn't get any better. That was 2 weeks ago and it has progressively gotten worse, but I was told that I waited too long to report it and they seem to be scrambling to deny my claim. They've refused to give me time off to see my own doctor as well. I've been going to work and barely able to do my job because of this. I'm actually working alone today, which is a bad idea considering I can barely walk.

Can someone explain my rights at this point?