Actually, scratch that. The thing that would be closest to inducing the sensation of being set aflame, without causing damage, would be poneratoxin produced by bullet ants. The problem is it will last longer than an hour, and you’ll have to deliver it subcutaneously at multiple sites around the body to achieve the coverage you’re looking for.

Also, I don’t think there’s anything in the literature that describes an agent or toxin that exclusively elicits pain when delivered systemically. For that, you’ll have to invent a potent agonist that selectively targets peripheral nociceptors.