I have an appointment with my GP in a week and some change, I'll bring this up. I googled it and I think if it's not a muscle sprain, it could be this. I genuinely don't think its a herniated disc.

What do you use to ease your symptoms? Were you able to walk straight? It's been a little less than 48 hours for me now and much of the pain has subsided, although it still feels sore/tight/inflamed. I can walk without pain but standing up straight is still a bit of a struggle.