How can you differentiate between skeletal muscle pain and real kidney problems?

I've had a dull pain deep in my back on the left side, where I think my kidney is. I dont know if I should have it checked out or if it is just a strained muscle....I have a toddler that I'm constantly chasing after, picking up, and some times not using my weight correctly on my back/legs. Are there other symptoms of kidney infections besides pain?