Thanks for your query.
It looks like a muscle strain
. Any strained muscle when stretched gives severe pain
I advice you to follow the below mentioned guidelines -
* Give adequate rest to the involved muscle group and avoid any movement that causes pain
* Ice packing once in every 2 hours over the affected area
* Moist heat application to relax the muscles
* Local application of muscle relaxant
medications as needed
I do hope that you have found something helpful and I will be glad to answer any further query.