HI Adam

Is the thigh pain on running near or on the site of the avulsed bone? If so it may be that the fracture is coming along but is just not yet set there yet for the rigours of sprinting - one of the most demanding activity for the muscle. It may just need a bit more time.

Another possibility - there is something tenuous about the healed site. It may be less than optimal - this would need looking into.

Another possibility: If it isn't over the fracture site but oer the muscle (eg a bit further down the front of the thigh), and sartorius is the problem it could be not only did you pull a bit of bone off attachment of the tendon, but the muscle or tendon was also injured. Tendons can take longer to fully heal but respond well to stressing them to an appropriate amount of activity - Goldilocks principle not too large and not to little - you will need some guidance with this

Go see a Sports?MSK physio. they can sort out the diagnosis of the problem.