Greetings, sorry about the pain. Not to worry you just have stiff hamstring muscle which is at back of thigh. As home care ice at back of thigh. Take a week off from work.
Next Steps
get to see a physio with knowledge about trigger point therapy and posture correction and your problem is solved 60% within 3 days and with recommended exercise by physio rest of problem is solved in 2 weeks. but keep doing exercise as advised by physio and for next 6 months do exercise to have permanent reliable relief.
Health Tips
if any questions do let me know