The new case is a man who didn't attend but is connected to a hen's party that took place in Byron Bay last weekend and is linked to a number of COVID cases in Queensland.
The new infection in NSW was recorded after 8pm on Tuesday and will be included in Thursday's figures.
Premier Gladys Berejiklian said four shires - Byron, Ballina, Tweed and Lismore in northern NSW - would now be limited to gatherings of 30 and revert to the "four square metre" rule and masks will be mandatory in some settings.
"It is our strong preference - it will not be mandatory but it is our very strong preference - that if you live in any of those four local government areas, that you don't travel outside those areas," she said on Wednesday.
"We won't be policing that but it is very strong advice ... if there is community transmission, we don't want it seeded to other parts of NSW."
There were no plans to close the NSW-Queensland border, nor plans to tighten restrictions further, she told reporters.
The COVID-positive man's household contacts have tested negative.
Ms Berejiklian warned earlier this week that NSW should brace itself for new infections after a three-day lockdown was imposed on Greater Brisbane.
Cases have also been identified as visiting Gold Coast and Toowoomba.
She also urged people in NSW to cancel any Easter holidays to Queensland, warning them they could get trapped there if the Brisbane lockdown was extended.
A number of public health alerts have been issued for venues in the Byron Bay area, which is gearing up to host thousands of revellers for Bluesfest.
Ms Berejiklian said NSW Health was working with Bluesfest organisers.