Daniel Scott-Wright suffered serious facial injuries, and his mother says he has since been struggling to cope with regular nightmares.
The four-year-old underwent a 30-minute operation at Queen Victoria Hospital, where he received stitches to his cheek and eye.
Strips were also placed on his nose to keep it intact.
His mother Rosie Scott said the dog, believed to be a Staffordshire bull terrier, had to be prised from Daniel's face during the ordeal in the kitchen of a friend's home in East Grinstead.
"We popped in for a quick coffee and we had only been there about ten minutes when it happened," she said.
"Daniel was throwing toys for the dog, but it wasn't going to get them. Daniel stroked the dog twice, then all of a sudden it went straight for his face. It all happened so quickly.
"At first, all we saw was blood pouring from his eye, then we noticed his nose. My partner had to hold it on until the ambulance arrived. I was getting really worried, because you could see it was barely hanging on."
The incident took place on March 17 but, two months on, his mother says Daniel is still struggling to recover from the attack.
Rosie, 20, of Woodbury Avenue, East Grinstead, said: "He has had a lot of nightmares over it. He woke up the other night, jumped out of bed and was shaking his leg saying 'put my leg back on'.
"He says he keeps dreaming that the dog is eating him. No matter how nice a dog is, he will not go near them now, he's too shaky. It's really upsetting."
Rosie, also mother to 18-month-old Callum, wants the animal to be put down.
"We've found it all quite traumatic," she said. "If I was to come face to face with that dog again, I don't know what I'd do.
"Daniel has been really shaken up, I'm just happy he looks the way he does, because it could have been a lot worse."
Sussex Police confirmed they received a report of a dog biting incident at a home in East Grinstead on March 17 and are continuing to investigate.
The dog owner declined to comment when approached by the Courier & Observer.
(This is Sussex - May 31, 2012)
