Yes it's OK to put mupirocin inside your nose and that's the recommended way of using mupirocin.
To use mupirocin in your nose put one half of the mupirocin medicine in each nostril.
After you've put the mupirocin ointment in your nose then gently press on the sides of your nose and rub it for about 1 minute which helps to spread the mupirocin ointment through your nose.
The medicine mupirocin is meant to be used inside your nose and so yes you can use it inside your nose.
Using it anywhere else will cause it to not work.
So make sure you put the mupirocin inside your nose for the medicine to do it's Job correctly.