As Deb says, since you were not hurt at work, the employer is not obligated to give you light duty work. If they don't have any light duty work, you could take sick leave or vacation time, but that's about it. The one thing the employer can't do is force you to your regular shift / work as it would be violating Dr's orders.
You are not being discriminated against and to be honest, if you saw a lawyer, it would probably cost you more money than what it's worth. Additionally, before you potentially interject a lawyer into the situation, I would think long and hard before doing so because at that point, you would probably be labeled a trouble maker, and it could really affect things down the road.
I know this is not what you want to hear, but just trying to help. This whole thing sucks and I'm sorry you're having to deal with it. Best of luck with this.
Regards,
Ex