Skin off my nose... in British common law, one is said to have the right to swing one's arms freely in the air, but that right ends where the other fellow's nose begins. Thus, when commenting on the action(s) of others, if another's action(s)do not bother you, it's "no skin off my nose".

My aged aunt, when asked how her health was holding up, would reply, "I can hear a flea fart and I can pick fly shit off pepper." When she met someone overweight, she would greet them with, "And what have you been EATING ? Everything ?"