I fell down stumbling on the dent on the ground. Was taken to ER. Now home with terrible pain in my shoulder, head, neck, wrist, knee. can I sue city?

You probably can't sue the city- but you can sue the owner of the property directly in front of the sidewalk, because they are responsible for maintenance of the sidewalk. The city can no longer be sued for sidewalk slip and fall accidents unless they created the damage to the sidewalk with construction, etc.  The dent has to reach the threshold of an actual sidewalk defect, and you have to be able to explain how you tripped on the dent- looking back at it and saying "that must be what I fell on" doesn't cut it.