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
In central England and across Scotland, any early cloud will clear, leaving warm sunshine for the rest of the day.
Marks & Spencer has unveiled another year of falling profits as the high street giant counts the cost of its transformation programme.
Philip Roth, one of the great American authors who won the Pulitzer for American Pastoral, has died aged 85.