You could have pulled a muscle or ligament in that area. Several muscles connect to the pubic bone as well as a big ligament.

Did you do any exercise yesterday or stretches? That is usually what does it to me - the groin stretch. I can't do it anymore.

Try to take some Advil or Aleve and use a heating pad over the area. It could take up to 3 weeks to settle down if it is one of the above things.