After the tooth that got a root canal and a crown suffered a blow, that tooth began to be sensitive and hurts whenever i chew or bite down. does this indicate i got a fracture?

Not necessarily: But would definitely suggest to let your dentist know and having it examined.

Trauma: Soreness may be due to fractured tooth, fractured bone, traumatized soft tissues. See the Dentist that did your root canal treatment for reevaluation. In the meantime, stay off that tooth. Bite/chew elsewhere. Nothing too hot/cold. Eat soft/high protein diet. Take anti-inflammatory pain meds such as Advil or Aspirin. But first, call your Dentist.