There are lots of things you could say in this situation. I would tend to avoid using taboo language in another language because it is so easily misused. You might say any of the following:
Mind you own business.
Get a life.
Whatever. (look up the appropriate hand gesture on Google )
Tell it to the hand because the face isn't listening. (hold the palm of your hand up in front of your friend's face when you say this.)
All of the above are a lttle impolite and you would need to have a good relationship with your friend to use them without causing upset.
You could aslo just say this:
Thanks for worrying about me. I'll keep your warning in mind in future.
I hope this helps.
Student or Learner