White, pin, or red oak sapling
The hairs growing out of the points on the leaves indicate a red oak of some sort, although it is difficult to identify at this stage (and not being familiar with oaks in New Jersey). Oaks are generally classified as red or white, with each classification including many species. Oaks in the red group have pointed leaves, usually with hairs on the tips and have acorns that take up to two years to develop. Oaks in the white group have rounded leaves and have acorns that mature in a year. There are other differences, but those are fairly easy differences to recognize. I would recommend trying to identify the oaks in the red oak group in close proximity to where you found the acorn seedling as it may be the parent tree! When the seedling loses it's leaves and grows next year's leaves in the form of a bud at the end of the seedling, you may also be able to identify it by the winter twig. Good luck!