oh gosh what were you doing? dead lifts or kettle bells?
I once seized my back doing kettle bell swings I will never forget that day I literally cried on the gym floor because I was so close to finishing my work out, I was down for the count for two weeks functional movement was a horror.
But I will tell you one thing from that day forward I focused so much on my form that I never had another days issue with my back so grow from this do you have a coach or someone who can spot you?