@alphabeta , lantus is basically a fast acting insulin which has had some stuff done to it to make it turn into a sort of jelly which then breaks down slowly over 18 to 24 hours.
You've likely not injected into a vein - you'd be on the floor in a few minutes - but once in a while, people do seem to inject near capillaries etc, the shot gets into the bloodstream and that jelly stuff doesn't happen and it just acts like fast acting.
So, I'd be inclined to view it in the same way as a bolus overdose, because lantus is fast acting if it's found its way into stream instead of jellifying, and if you've managed to get yourself past that initial drop, I reckon you'll be fine.
But it's an uncertain and unusual situation, so definitely agree with the other posters - call yr emergency services.