'Honey Boo Boo' Star's Extra Thumb Went Thump

'Honey Boo Boo' star Kaitlyn Cardwell is healthy and recovering after surgery to remove an extra thumb.

Kaitlyn -- Mama June's 4-year-old granddaughter -- was born while the show was still on-air ... and her extra digit became a big topic of conversation. Kaitlyn's mom, Anna, tells us she made the decision to have the thumb removed to thwart medical issues and bullying.

Kaitlyn will wear a cast for 6 weeks ... but it's definitely worth it.

It could have an adverse effect on her cheese ball intake ... just ask Honey Boo Boo.