KRISTEN Stewart headbutted Taylor Lautner while filming a scene for Twilight: Eclipse – but it was an accident!

The script called for Lautner to grab Stewart from behind as she ran up a stairway, then quickly pull her toward him.

But just as the buffed up 18-year-old turned Kristen around, she accidentally slipped -– and her head banged down hard on his nose.

Instantly, blood gushed from Taylor’s nose as the director — fearing it was broken — called a halt to filming, according to American tabloid the National Enquirer.

Ice packs were ordered immediately, and the on-set medic quickly checked for damage. Taylor’s nose wasn’t broken; just badly bruised.

Source: Show Biz Spy