how is it to hide what you are preparing for, particularly a competitive test, in islam?

Question

I'm currently studying for the Central Superior Services (CSS) test, but I don't want anyone to know about it. I am a 3rd year MBBS student at a government medical college in Pakistan, but recently I have started preparing for the CSS exam. I'm keeping it a secret from my colleagues, who have no interest in it and I don't want to boast about it. I am wondering if keeping this a secret is considered sinful in Islam or not