A man punched his girlfriend’s 3-year-old autistic son in the face in The Bronx late Saturday, police sources said.

The suspect struck the tot around 10:40 p.m. in an apartment building on University Avenue near West Tremont Avenue in Morris Heights before taking off, according to police.

The toddler was taken to St. Barnabas Hospital with non-life-threatening injuries, police said.

His attacker was still on the loose early Sunday.