NSW teen hit with gun during home invasion

A teenager has been injured in a home invasion in Sydney's west.

Four people in masks, one armed with a firearm, are alleged to have forced their way into a home on Campbell Hill Road in Chester Hill about 1.15am on Thursday.

They hit the 16-year-old boy on the head with the firearm before stealing a sum of cash. The teen was taken to hospital to be treated for a small head wound.