That's a bullshit thing for him to do. How much of a "boss" is he? Like a high up or just a foreman? If that's a foreman, report it to the company owner, that should be grounds for immediate dismissal. Trust me man, you don't want to work for a cheat. If he's willing to cheat on a fucking OSHA 30 cert than what else is he cheating on. That's opening yourself, your boss, and the company to a lawsuit if an accident happened and OSHA investigates, which they will.

I'd weigh your options man, but project engineers/bidders are in high demand, you could get a job just about anywhere. What your boss did would be a huge red flag to me about the company culture in general. I wouldn't want to work there. But if its just that one guy, report it to upper management.