If you are looking for a way you can force your employer to honor his promises without the involvement of the legal system, there isn't one.
You have two choices. You can contact a workers comp attorney/your workers comp carrier yourself, possibly get the bill paid, and deal with the employer, or you can do nothing, not get the bill paid, and continue your relationship with the employer as is. There is no door number 3 where you do not contact anyone but the employer is somehow backed into a corner and pays your bill.