"It's too late to change the plan now," Harry told Hermione. "We haven't got time to send Charlie another owl, and this could be our only chance to get rid of Norbert. We'll have to risk it. And we have got the invisibility cloak, Malfoy doesn't know about that."
They found Fang, the boarhound, sitting outside with a bandaged tail when they went to tell Hagrid, who opened a window to talk to them.
"I won't let you in," he puffed. "Norbert's at a tricky stage –– nothin' I can't handle."
When they told him about Charlie's letter [Charlie’s friends can carry the little dragon away from Hogwarts to his place], his eyes filled with tears, although that might have been because Norbert had just bitten him on the leg.
"Aargh! It's all right, he only got my boot –– jus' playin' –– he's only a baby, after all."
The baby banged its tail on the wall, making the windows rattle. Harry and Hermione walked back to the castle feeling Saturday couldn't come quickly enough.
(Harry Potter and the Sorcerer's Stone)
Is the bold-faced part a double negation or the dialect of ‘I can’t handle anything'? I guess semantically the latter is more probable, but I can’t be sure.