A tongue biopsy is not painful as you will be put to sleep or the tongue at least numbed.
So you will not feel any pain during the tongue biopsy.
You might feel some discomfort after the anesthesia wears off or the numbing agent wears off but it should go away within a few hours or less.
Before the tongue biopsy you will generally need to avoid eating or drinking anything for several hours.
However while the tongue biopsy is not painful the tongue is very sensitive so a needle biopsy may be uncomfortable even when numbing medicine is used.
The tongue can be tender or sore, and it may feel slightly swollen after the biopsy.
You may have stitches or an open sore where the biopsy was done.
Most tongue biopsies are performed under local anesthetic which will involve an injection of anesthetic into the area where the biopsy is going to be taken from.
The injection is a similar medication as that used by your dentist.
It will only make a small area of your mouth numb.