[6] Nicholls and Barnett won the doubles title at the Championnats Banque Nationale de Granby, defeating Harriet Dart and Rosalie van der Hoek in the final which went to a deciding champions tiebreak.

[7] At the 2023 Wimbledon Championships, partnering with Jonny O'Mara, Nicholls reached the semifinals in the mixed doubles, losing out to eventual champions Mate Pavić and Lyudmyla Kichenok.

[8] Alongside Olivia Gadecki, Nicholls won the doubles title at the ATX Open, defeating Katarzyna Kawa and Bibiane Schoofs in the final.

[12] At the Billie Jean King Cup finals in November, Nicholls and Heather Watson lost to Mihalikova and Viktória Hrunčáková in the decivisve doubles match as Great Britain were eliminated in the semifinals by Slovakia.

[13] Partnering Henry Patten, Nicholls reached the mixed doubles semifinals at the Australian Open, defeating top seeds Andrea Vavassori and Sara Errani in the second round[14] and then Jackson Withrow and Irina Khromacheva in the quarterfinals.