Hi, thanks for using health care magic
The white area of skin may be old skin that is going to come off.
Signs and symptoms of infection are : (1) increasing temperature (2) pain (3) redness
(4) increased warmth of the area (5) discharge.
It may be best, since the top aspect of the thumb has been removed, to have it assessed by your doctor.He or she would be able to determine what , if any , dressings are needed.
I hope this helps