This is 30 days post FUE session which consisted of 3900 grafts. Is this an infection or something worse? (photos)

If you already saw your doctor for an examination and your doctor says it is not an infection, you should trust your doctor.  If you do not trust your doctor it is best to see another doctor for an examination.

just wash your hair properly with a high pressure massage . it does a good mechanical cleaning job .
if you need you can use a soapy wet towel for massage the scubby area, it Works very well to remove dirt.

at 29 days I would expect all of the crusts to have been shampooed off. Follow the directions I gave you earlier