Honestly, I'm surprised they didn't offer some sort of apology when it first happened, and that a store manager didn't try to speak with you after the incident.
Definitely contact them to let them know what happened and that they should do something to prevent it in the future. That's as far as I'd take it, though.
I was injured in a Starbucks once. Two older women were acting like teenagers, jostling each other around, and one slammed into the display rack with mugs on it. The mugs shattered when they hit the ground, and a chunk of one ricocheted straight into my big toe, which immediately started gushing blood.
One of the women responsible told me that I should sue the store. I tried to be polite, but I told her I didn't know why Starbucks would be responsible for two grown customers acting like children.
The staff was fantastic in helping me get patched up, and I suggested that maybe putting displays like that (free standing in the middle of the area right next to the register) so close to where the line forms wasn't a good idea, but that was as far as I needed to go.