Don't be ridiculous about trying to break your own foot. That's crazy.

Just be an adult and go have your foot checked. If you're not gutsy enough to have it checked on your company's bill, you can pay for it outright. A doc's visit and a foot X-ray shouldn't be more than $200, and it may be a lot less. Your boss is trying to save money, but if he fires you for going to check on a work-related injury, the folks at the Occupational Safety Hazard Administration will be happy to listen to your complaint, as will the workers' compensation authority in your state. You need to have the injury checked within 72 hours, too, so you need to go tomorrow.

Just do it. He doesn't have the right to try and intimidate you not to check on your own health, and frankly by letting him get away with that, you're now sharing in that irresponsibility, too.