Hi Mark. I am currently off the bike due to an over the bars crash resulting in a back injury.
The symptoms I had were/are a sharp pain down my left leg after being seated for a few minutes. Saw my own physio as nhs was a 12 week wait. Anyway, i had a bulged disc which was aggravating my sciatic nerve. Was told 4 months to get better, but after seeing physio, doing stretches and plilates after 2 months a huge improvement.
My advice, docs, ibupropen and see if you can get to a physio asap. (£35 -40) per session near me
Hope its better soon mate.