He replaces Fred Clapperton, who managed The Clock House kitchen for the past four years.
It was announced last month that Clappterton was leaving to take over as head chef at The Seren Collection’s Coast Restaurant in Saundersfoot, Wales.
Nicholson joins The Clock House from Frances Atkins' The Yorke Arms in Nidderdale, Yorkshire, where he also served as head chef.
Prior to that he oversaw the stoves at the Storrs Hall hotel's Lake Edge Restaurant in the Lake District.
"The Clock House already has an excellent reputation,” says Nicholson.
“The team both in the kitchen and restaurant have created a great dining experience with a relaxed, yet highly professional, environment.
“I look forward to bringing its guests new dishes, and creating a more inclusive, continuously evolving menu.”
The Clock House was originally opened as Drakes by chef Steve Drake and his then wife Serina in 2004, and was awarded a Michelin star within its first year.
Steve left the business in 2016 after separating from his wife, and it was subsequently rebranded as The Clock House by Serina, who continues to run the restaurant.
It lost its Michelin star in the 2017 Guide following Steve's departure, but regained it a year later under Clappterton.