Hello
Buttocks pain which travels down the leg, indirectly suggest affection of sciatic nerve. ( as per the given info)
Sciatic nerve can get affected with many conditions but most commonly because of slipped disc.
Next Steps
Take complete bed rest for 2-3 days like 23/24 hrs and see the pain intensity reducing or not.
Also start supplements for low vit D. Cap uprise d3 once a week for 6 weeks
Health Tips
Avoid bending forward, long sitting, low sitting for 2-3 months till the injury heals on its own.
OTC painkillers can be taken if pain is not tolerable.
If after one week pain is not going down please consult orthopaedic spine surgeon near you.