It's kinda hard to decide how serious is the pain. However, since you haven't mention pain radiating downward to buttock or the legs, i'm assuming it doesn't involve any nerve problem.
I would suggest the following :
1) if u think there is a partly muscle problem, u could always use hot pack to relax the area then have someone to gently massage those painful area. (unless you have any open wound, tumors , cancer, or infected problem with risk of spreading, then DON'T heat and massage)
2) there is a technique for simple back pain. try bending forward until you have moderate pain at moderate speed repeatedly , say maybe 10 times. pay attention to the quality of pain. if the pain gradually improves or painful area decreases as you repeat bending, then it means it is a suitable movement to do as an exercise for your back pain. If u notice the pain hasn't change a bit, but you are able to bend down more and not getting more pain , then it is also good to do as an exercise. On the other hand, if the pain worsen or pain starts to radiate downward, then stop immediately.
if bending forward doesn't help, you can try bending backward with the same approach.
Base on experience, i would guess bending forward is more likely to help you. Keep in mind that this is based on the limited information you have provided and without a complete assessment.
As an exercise , you could do it 3 times of 10~15 time each, with small rests in between as needed. ~ 6 to 8 times a day.
You should try to resolve it within 6 weeks , because the longer you have the pain the more likely it will become a chronic problem. seek physio treatment if it doesnt get better.
**What I described in no.2 is a way for you to test what exercise to do that may help you. Do not go straight ahead and do the repeated bending without carefully monitor and think about how your symptom changes when you are testing it.