Keep your back moving. Get back on your feet as soon as possible.
Do not do any lifting. If you do lifting, you are likely to strain your back.
Take painkillers and anti-inflammatories. Stick to recommended dosages and read the packet to ensure they are suitable for you.
Be careful bending your back, this puts a lot of strain on your back which can make the problem much worse.
Try cold and hot therapy. Apply icepack wrapped in a towel to the base of your spine for 5 minutes, follow with 20 minutes of heat. Hot water bottle wrapped in a towel.