Ice to reduce the inflammation. If you put heat to it that increases the blood flow which increases the swelling. Later on, when it has calmed down, you might try heat, but not for a good while, imo.

I have hardly any trouble with mine, anymore, after years of debilitating pain and meds/adjustments/massages/acupuncture/ etc. I am doing a modified qi gong as seen on Lee Holden's Qi Gong for Seniors. It makes a HUGE difference. THIS ONE is specifically for lower back pain.

The other thing I use, frequently, and intensely IF I get hurt is Zheng gui shui which REALLY works!! I always have this on hand.