Hi,
Welcome to the ehealthforum. I am glad to help you out. The few possibilities which I can think of in your case is a muscle strain. This commonly occurs due to the overstretching of the muscle tissue resulting in the damage to the small blood vessels. Using some OTC painkiller for a few days and rest should help improve the symptoms. Also apply warm compresses and some topical muscle relaxants.
If the symptoms persist then please get it seen from your doctor. I sincerely hope this information helps. Take care.