Weird wobbling at low speeds after back bumper came loose.

I was driving on the highway when I randomly heard a loud dragging noise coming from the back bumper. When I stopped to check the car out I noticed the back driving side of the bumper came loose and was lower that it should be and the inside part of the bumper was hitting the tire. I cut the plastic piece that was rubbing against the tire but now I feel a weird wobble coming from the back driver side when I drive slow. When I drive fast the car seems perfectly fine with no wobble at all. The tire looks fine and still has enough air. Everything looks fine except the bumper. The steering wheel seems fine as well. No weird jerks or wobbling from the steering wheel. I didn't hit anything or drive over a pothole. The bumper just randomly came loose. Any idea what the wobbling might be? The bumper has been damaged for about a year or 2 after a old car accident but this has never hapoened before. Is it smart to drive the the car still until my day off before I can take it to a shop?