I've been lifting consistently for around a year and have been fortunate enough to not have any injuries. Yesterday while squatting heavy (it was a rep PR) I hurt my back on my last set. It was a mental thing - I was lifting the weight fine but on the last set my mind kept yelling at me "it's heavy!!!" I lost focus of properly bracing my core during the descent, and let my back round out a bit - just enough to feel a tweak in my lower back.

It wasn't bad - I was able to complete the workout with no pain. I was feeling it later though so I went and got a massage. Today I'm still feeling it, which has me worried.

So - how do you know if you have a real injury or just a "tweak"? Should I just let it rest until I don't feel any pain at all? Keep training while avoiding a load on my back? Or just do my normal routine with lower weight?