He's an absolutely beautiful boy, but he has a horrible case of scaly face mites
I'm glad you'll be taking him to the vet, the vet should prescribe Ivermectin, which is the medicine used to treat this illness. One drop between the wings (directly on the skin) will start to clear it up.
The thing is, mites are extremely contagious to other birds and they can remain in the cage for a long time, so you should keep the cage extremely clean. Take out and throw away any toys with fabric or rope, as the mites will burrow into them. Clean all perches and toys with hot water and vinegar to be sure there are no mites, and for the first few days of the treatment, I might even take the entire cage outdoors and hose it down. If this isn't practical, wipe down the entire cage with hot water and vinegar (put the budgie(s) in a travel cage first).
If there are any budgies he's been into contact with, all of them need to be treated in the same way, and they also need the Ivermectin.
Despite everything you need to do to prevent a re-infestation, it's very easy to treat and with the proper care, he'll be back to normal in no time
Best of luck with your handsome boy, please keep us posted on how he's doing!