I'm no expert but had a similar experience a few years back. The pain was so bad I couldn't work out. I went my doctor, to check for a hernia he didn't find one, he refered me to a specialist who didn't find one either. I had to stop working out, it hurt to even sneeze. I got fat from not working out, went to a hernia clinic, was told I had a hernia, but needed to loose 30 pounds before surgery. The pain got a bit better, so it took my time losing the weight. About a year later I started working out again, and then the pain came back, right as I started to get heavy into ab work.
I had lost enough weight for the surgery, so I went back to the clinic. Two doctors examined me and said it was a groin strain. Where were those guys a couple of years earlier? They told me to rest it for a 3 or 4 weeks, and soak it in a hot bath. Of course I didn't listen, as it was the start of ball season. So I took a week off of all exercise, soaked, and stretched it more. I upped my fish oil consumption, and went to an ART specialist, and I was able to get back to lifting and play ball all summer, with minimal discomfort It is still a bit tight, but only bothers me if I do lunges now. My advice would to just go with the rest and stretching. Then when resuming activities, just make sure to stretch it out. I would start taking a fish oil product immediately to handle the inflamation.
I personally just ordered some of the new Biotest Flameout! it looks really good, but if money is an issue a cheaper product like Costco brand will do. A good ART specialist can also do wonders if there is one in your area, but most of all you are going to have to rest it, to give it a chance to heal up. If it is a hernia it definetly won't feel better with rest.