The Geordies trailed to a Dean Shiels goal before Andy Carroll fired them level after 67 minutes after which Donny then missed from the penalty spot.
Zurab Khizanishvili was then shown a straight red card for violent conduct in an off-the-ball incident and it looked as if a point would be all United would get until Nolan drove in from outside of the box to settle the issue
With Chris Hughton already assured of becoming the latest custodian of the St James' Park hot-seat, the former Spurs stalwart had more pressing problems to deal with - to get Newcastle's promotion push back on track.
Since their crushing 4-0 win at Ipswich Town, United had managed just two points from 12, courtesy of home draws with QPR and Bristol City but followed more alarmingly by defeats at Nottingham Forest and Scunthorpe United.
During this uninspiring run, Newcastle had also relinquished top spot and allowed a clutch of clubs below them to claw back their points advantage.
But Donny had not read the script and forged in front after 18 minutes through Shiels who found himself perfectly positioned inside the box and drove straight through the middle to leave Steve Harper well beaten.
The home crowd were left stunned and it could have been even worse when former United trainee James Coppinger had a 20-yard effort saved by Harper.
With the home supporters growing restless and with little to shout about Newcastle were a pale shadow of the side that started the season so excitingly.
Marlon Harewood finally brought a save out of Neil Sullivan with a header on the half-hour mark and Jonas Gutierrez, who never looks like scoring, saw one of his customary efforts fly over the top.
It was hardly surprising that jeers reverberated around the ground as a dejected United trooped from the pitch at the break.
There was more purpose from United after the break and they deservedly equalised through Carroll when he latched on to Danny Guthrie's cross.
Khizanishvili's departure looked as if it would mean the game would end up all-square until Nolan's last-gasp strike took Newcastle back to the top of the Championship.