What did I do?
 

The other day, I was working out with resistance tubing. I used a lightweight caribeaner to clip the tubing to a metal gate at about the middle of the tubing, and used the handles at either side to stretch the tube out with my arms.

Well, I was facing away from the gate and stretched the rubber out, and the caribeaner slid off the top of the gate and nailed me right in the back of the head. I immediately saw some stars/static and silver streaks, and heard ringing in both ears. These issues dissipated within a few seconds.

After this happened, I promptly put up my things, went back in the house and carried on with my day without any issues. The resistance band was about a 90lb pull, if that matters. I feel fine and I don't believe I experienced confusion, amnesia or headache at all.

Should I be concerned? Was that just one of life's bumps or should I be checked out?

No, you should not be concerned. This might barely be considered a sub-concussive impact. It would be a concern if you did it 100 more times.

I think you meant to say a 19 pound band. That is the most common heaviest resistance band.

As your considered, this was just one of life's many bumps.

A bit of skin soreness at the impact site would be expected.

Be grateful you were looking away. It could have messed up your face.

Have you considered using TRX style equipment instead ? They do not have the risk of snapping.

The band was a remnant of my pitching days in highschool, it has a pretty high resistance.

I'll look into TRX, thank you.

I've got both tube type that top out at 19-20 ( I see now one company sells up to 40#) and flat bands that top out at 20 to 30. My shoulder therapist gave them to me. But, I see a company makes a 65-100 and a 150-200 flat for leg strengthening. Ninja style cross training is getting pretty extreme. They could give you quite a bruise but the carabiner would be too light to cause any substantial force without a bone injury. But, OUCH. That ouch can cause the visual symptoms just like a hard sneeze can.

That makes sense. Perhaps the tinnitus was the result of bone conduction.