Can you tell me does the pain radiates down to your knee and then to toes?
Is the pain intense after long hours of work or after any strenuous physical exercise?
What I feel is either, because of your lower back strain, you might be having Sciatica.
Working for long time due to blood stasis, there can be pain, but not so intense.
Any injury in thigh could cause similar symptoms.
I think you should meet neurologist or an orthopaedician at earliest, if it is annoying you a lot.