Bison Molar Fossil
200,000 years old (Pleistocene) to around 10,000 years old (Pleistocene/ Holocene boundary)
North America, New Jersey
Measurements: 2" long, 1 3/8" wide, depth 1/2"

Both Horse (Equus) and Bison (Bison antiquus or Bison occidentalis) are somewhat common Pleistocene era finds along the North American Atlantic Coast. To distinguish between the fossils there are a few things to consider:
Bison teeth are typically shorter, narrower towards the base, and have short root lobes and grooves.
Horse teeth lack significant root lobes and have a ridge.
The chewing surface enamel folds are highly complex with zigzags in horse teeth compared to simpler folds in bison teeth.
Bison molars are generally narrower and upper bison molars have a short ridge.
Bison teeth are characterized by their high, crescent-shaped cusps and a distinctive vertical enamel ridge called a stylid.

I believe you are correct in identifying this fossil as Bison in origin. This appears to be a molar. Bison molar fossils can range widely in age, and I am unable, from images, to give an exact species or age verification. The have provided a general age range and an approximate average of the FMV for such examples. You could further explore your find by requesting an in-person appointment with a regional natural history museum specialist. Often, these organizations will have select days open for the public to bring in their discoveries for assessment.