It was the home side who had the first real chance of the match after five minutes when Adam Clayton struck from outside the box, but he fired wide.
Meanwhile, Lewis McGugan rattled the post for Forest moments later in a lively opening period between the two sides.
McGugan remained a threat early on, twice coming close to breaking the deadlock with efforts either side of the 10-minute mark.
Lee Novak and Jordan Rhodes began to link up for the home side in the latter stages of the half, but it remained level at the break.
Novak continued to come close for Huddersfield early in the second period, while Rhodes headed wide just before the hour mark.
Forest evenutally look the lead, however, after 68 minutes when Cox advanced on goal before slotting it home from close range.
Rhodes continued to come close for the home side in the latter stages of the 90 minutes, and they were awarded a penalty in the final moments of normal time, which the striker converted to snatch a point.