Baby had thrush. After nystatin treatment we still find white patches in mouth on cheeks that can we wiped away. Can this be milk residue?

It could be. Infants and formula as well as breast milk can often be found on the tongue and on the oral cavity and be misconstrued as an oral thrush. Nest to let the dr. Examine your child again and assure the thrush (if it ever was thrush) has resolved, and all it is now is milk residue. Best wishes.
Thrush. If white patches can be wiped away it represents milk residue.
Thrush. Yes, usually if you can wipe it away it is likely milk residue. But if you have concerns have your pediatrician check it out.