Hi there,

As much as you may not have pain in your lower back the potential sources of symptoms are either your lower back or your hamstring/ gluteal. As it appears that you have some understanding of anatomy it may be a facet joint irritation which may explain the referred pain down the front of your thigh and why it is aggravated with running but dulls off as you run further. Lumbar rotation stretches might help however as it does seem to be limiting your function i.e .running and it has taken more than 4 weeks to resolve I would suggest seeing a manipulative physiotherapist. In this advice I do assume that it is not a hamstring or gluteal tendinopathy as they are more than unlikely to refer but one cannot predict what the human body does with injury.

With this there is a lot of information I do not know and would have asked i,e, any change in behavious prior to going on this running? i.e. increased sitting time ? also if there was any previous injury i.e rolled ankles or history of back pain and that kind of thing.

Hope this helps. Definitely seek some professional advice though if it hasnt resolved by itself over 4 weeks.