Often when someone gets an injury, particularly when it is in the back, there can be spasm/tightness/cramp sensations.
It may not be obvious but what is felt may have nothing to do with the actual injury as much as what the body is doing to try to protect itself. You would not think that you could injure such a big area with the small movements or seemingly innocent tasks that started things off and you would most likely be correct!! This is a protective mechanism that works much the way a cast does..things that can't move have a chance to settle down and heal.
Unfortunately the body does tend to overdo many things and the discomfort is far more that most of us want to put up with. I have fortunately (unfortunately!!) felt this sort of thing when I have been involved in tackles playing rugby. A hit that didn't seem to do much might have irritated things to the point that I could not move my neck for a week or more. Today I don't have to suffer quite as much as I know that with a couple days rest and the use of cold packs/heat packs/liniment/massage/acupuncture/electrical stimulation I can get the spasm to ease and try to assess what is the underlying problem. Sometimes it is just shock/reaction to pain and the problem goes away quite quickly. Other times it has been more serious and I have had to deal with the problem over a longer period of time. In either situation I have been in control, sufferred less anxiety about how my body has behaved and been able to get back to my games in optimum time. Hey at 51 I made it through 19 rugby games this season without having to miss any play for most of the season.
Cheers from the UK!!