the first thing i would do is cut those long nails so you can actually use your fingers better. and theres no way they could arrest you for that. first of all, they don't know what "substance" is inside the balloon. They would have to get it lab tested and everything.
look, go to the doctor, and they are either just going to throw it away, give it back to you, or you can take that shit and throw it down the drain before they can do anything. either way, its your health first, fuck the law.