I had this happen to a hammer, my clowns host in it and at night they grab a hammer or two so they don't get blown around in th current. one night when I turned the moon lights off it spooked one of the clowns and she pulled off the hammers she had in her mouth the next day there was a bubble where the injury was lasted a couple weeks. I would guess that every time you poke at the bubble it is being re-injured and blows up larger to protect it self. Just leave it be and it will go down by it's self.

Bill