back painfull

Hi just I want to ask this question I hope I can find an answer for it.

Last week I was working in childcare because Iam a childcare worker (what happen in that day as udjaly I came to worke at 8:30am I was alone in that room I work in with 12 childrens and I do work in age between 3and 5 years old as I saw 2 childrens fitting and I tried to seperate them and lift one child away and Iwas trying to lift the other as sudently felt pain in my lower back).

I went to the doctor and she told me to take a rest for 1 week but after one week I did back again to see a doctor because I m still in pain and the doctor advice me to do X -ray I done it and this is the resulte(There are four lumbar type vertebrea with sacralization of l5. The disc are all well maintained.The neural arches are intact. The facet joints show minor degenerative changes at l5/s1.The SI joints are normal).

So what is that mean can anyone please tell me if this thing could cause from liffting childrens.