I wouldn't worry too much about it. My reagal used to do the same thing with my seabae. Only, he actually did touch it from time to time. I think he though he was part clown fish.
BTA's aren't really "fish eaters" at the size most of us keeps them. The tang will probably feel a sting and move away, and if yours is a dumb as mine it will keep getting stung until it learns.