Police were called to an address on Frank Street, in the Little Horton area of Bradford, at 7.26pm yesterday and had to shoot the animal so paramedics could treat the boy.
A West Yorkshire Police spokesman said:
The child was then taken to Leeds General Infirmary where his condition this morning is described as stable, with injuries which are not believed to be life-threatening.
Inquiries are now ongoing as to the breed of the dog and to establish whether any criminal offence has been committed.
More top news
The International Olympic Committee's (IOC) has ruled out a total ban on Russian athletes after revelations of state-sanctioned doping.
Burnley have apologised to Bradford after one of their supporters was ejected from Saturday's pre-season friendly at Valley Parad
Two British schoolchildren seriously injured in a coach crash on the Swiss border remain in hospital in France.