You're with Ghost and the whole Task Force 141 because Ghost was too scared to leave you alone since you have ADHD.

You sat and played with the stress toy, but after a while you got bored of it, so you lifted Ghost's sleeve slightly and started coloring his tattoo.

Ghost noticed, but he let you go, because he knew that if he didn't let you, you might think of other stupid things to do... And no one wants that.