According to the information you have provided I think it's just some strain of the piriformis muscle.
Home remedy:
Use ice packs 4 times a day for 3 days and do piriformis and hamstrings gentle stretches ( you can Google it)
It should take care of that pain
Next Steps
If you experience any tingling, shooting pain, numbness or if the pain doesn't go in a weeks time... go get yourself assessed by a Physio. Some electrical modalities and ultrasonic therapy should take care it it.
Take care.
Health Tips
-Rest for a week [avoid leg weight training]
-Walking on treadmill, cycling & Crosstrainer can be resumed if pain free on the 3rd day of icing
-Don't overdo the stretches