Whatever you do, do not overstretch, or really stretch out your back at all. shyt will set you back.
The best thing you can do is walking in between periods of rest. Be careful to not sit or lie down for extended periods of time.
Core exercises, like lying hip thrusts or superman pose exercise (arms in front), will help tremendously. No situps, hold off on planks until you are back to normal.
If it's just a strain, it will slowly get better. If you herniated a disc, you're in trouble. A huge part of back injuries, is that they can be really discouraging. You can feel great before going to bed, and wake up feeling like you're back at square one. It takes time, but it will get better, don't get too down and remember to go on walks to keep yourself active.
Use your arms when you have to get up from bed or from sitting down.
When you return to work, use a belt, and practice safe lifting techniques. Belts do not replace proper lifting.
I would also speak to a supervisor about filing a work injury report. It's better to have the paperwork ready in case you have to go to see a doctor, instead of reporting it after the fact.