This should be surgically repaired. Your regular vet may be able to do this or they may refer you to a veterinary surgical specialist or a veterinary opthamologist.
You can read here about how the surgery should be done
http://marvistavet.com/html/cherry_eye.html
so you can discuss with the vet you choose what method they will use for the repair.
This sort of surgery can be done in a young pup so the age to do it will depend on the vet chosen. Some vets are less comfortable with anesthesia on young pups than others so while some vets may be willing to do it now others might want to wait until 12-16 weeks.
I'd start with your regular vet and suggest if they can't do it that you get a referral from them to the specialist they recommend.
Hope this helps you!
Dog Expert:Rescue, Train,Breed,Care
30+ yrs dog home vet care & nursing, rescue, behavior&training, responsible show breeding, genetics