The Red Dragons had been seeking to follow up week's brilliant win over League Two MK Dons with another three points.
However, soon after the restart, Nix's shot was deflected by Steve Evans past his home keeper Gavin Ward for City's equaliser.
The home side had taken the lead in the 38th minute when Donovan Ricketts could only get a hand to a Neil Roberts scorcher and a mighty scramble followed, with Roberts finally getting a touch to put the home side in front.
In the 66th minute Eddie Johnson was carried off with a leg injury and earlier Omar Daley was lucky to only get a yellow card for a late tackle on Wrexham's Chris Llewellyn.
Daley, who was always a danger, forced a brilliant save from Ward with six minutes to go and in a final flourish the home side's Jeff Whitley shot over.
Michael Proctor then had a shot saved by Ricketts and it took a desperate tackle by Matthew Clarke to halt Proctor when he was clear.
Both sides had chances in a lively first half before Wrexham took the lead. Nix was slow to react when Ward fumbled a Paul Heckingbottom free-kick and then Lee Bullock hit an effort over the Wrexham bar.
Wrexham gradually got back into the game and Drewe Broughton hit the bar with a tremendous shot.