Loy was injured in a challenge with PNE defender David Gray early in the first half, which led to a nine-minute delay.
"I don't think we're going to see much of Rory over the next few weeks, possibly even months," boss Greg Abbott told BBC Radio Cumbria.
Loy had scored four goals in 25 games for the Cumbrians so far this season.
"I really can't believe how much support I've had and how much it has helped and inspired me to get back," Loy posted on his Twitter account.
United have had a string of injuries in the striker department this term.
Dumfries-born, Loy began his career at Kilmarnock, but joined Rangers without making an appearance.
Despite spending three and a half years at Ibrox, Loy made just two appearances for the Gers first team, spending time on loan at Dunfermilne and St Mirren before joining Carlisle in January.