Assuming no loss of feeling, control or numbness it’s likely to be muscular, gone into spasm. Get the best painkillers and anti-inflams you can find and get to a GP if it doesn’t get any better in a day or so. Im a little jaded as I had a similar issue and have been passed from medical pillar to post with no-one giving me an answer but having to deal with increased insurance costs for travel due to the repeat doc visits.
I’ve been to two physios, including one very prominent sports physio that works on local sports personalities. They gave similar descriptions but conflicting advice. Following either’s advice seems to make things repeat more frequently and following the sports phsio’s advice seems to rapidly increase my injury rate. I’ve re-assessed my own back from an engineering/common sense point of view and do the exercises/stretches that I think make sense and it seems to be vastly improving in strength.
One suggested I was over-curving my lower spine and that was causing pressure on the nerves, that I should attempt to straighten my lower back more when bending/using it. This immediately throws it into spasm, however they did point out that I have hamstrings so tight they are like guitar strings so i’m trying to stretch those out.
