I don't think that this is anything major and you shouldn't worry too much about it just yet. Give it a few more days at least. It probably is a pulled, irritated muscle. This kind of thing happens all the time. It can take it a week or two too fully recover.
I would say if after the weekend it is still as bad as it is today then you should make the effort to see a doctor and request an x-ray. Only you know how it feels. If it's really bad than you may want to go sooner. It could be other things but in my experience and so on I think it's a pulled muscle. I'm not an expert so don't quote me on that or anything!
Things you could do for relief is icing and or heat. Sometimes alternating it is a good idea. I don't know if you are taking any meds right now but Ibuprofen is an anti inflamatory and it may help you. To find out if it's something you can take you should call your pharmacist. Also you could mention it to them. Pharmacists are quite often very helpfull and can give you suggestions and advice.
Good luck. I hope that I have helped you out a little bit. Let me know if there's anything else I can do. Take care. Keep me posted. Beachgirl.