Bruce Rourke's collie attacked the girl, who cannot be named for legal reasons, at a Scotmid store in Castle Street, Tayport, on 5 January..
Rourke, 57, from Tayport, pleaded guilty on summary complaint to a charge under the Dangerous Dogs Act.
Dundee Sheriff Court heard the girl was with her mother, who was using an ATM outside the shop.
At the same time Rourke was tying up the dog a few feet away. The animal lunged at the girl before biting her on the body.
She was taken to Dundee's Ninewells Hospital and given antibiotics as a precaution but suffered permanent injury.
Sheriff Alastair Brown deferred sentence until next month and said he may make an order for the dog to be destroyed.

Residents were evacuated from Kirkennan Drive, Dalbeattie, on Tuesday afternoon after the weapons were found while a house was being cleared.
A team from the Royal Logistic Corp examined them and found them to be inactive.
The A710 (Port Road) through Dalbeattie was closed for two hours during the alert.
A spokesman for the Royal Logistic Corp bomb disposal team said: "The ordnance was fully examined and found to be inactive. It has been removed from the house and we have taken it away."
A "dangerously out of control" dog could be put down after it bit a 10-year-old girl outside a Fife shop.
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Bomb disposal officers have removed a shell and hand grenade from a house in Dumfries and Galloway.