The Only Way Is Essex star had been enjoying festive drinks in London with co-stars Frankie Essex and Lauren Pope prior to the incident.
Sims was pictured getting into an ambulance at 7am with Essex, holding a self-made bandage around her bleeding hand, the Daily Mail reports.
A spokesperson told the paper that Sims sustained the injury when she was trying to leave the Hoxton Pony via a fire escape, claiming that a staff member had accidentally closed the door on her hand.
Sims was initially taken to University College Hospital in central London for treatment, where the reality star was ushered inside under a red blanket with blood dripping onto her leg.
The trio had begun their night with dinner at Nobu Berkeley, before moving on to The Hoxton Pony where Pope was DJing. They tweeted fans throughout the night.
"Big hugs for @Chloe_Sims today, my poor lil pops!! xx," Pope tweeted on Saturday afternoon.
> 'TOWIE's Chloe Sims calls police after Twitter threat
> 'The Only Way Is Essex' cast celebrate finale at London nightclub: Pictures
Watch the series three trailer for The Only Way Is Essex below: