this seems like something of acute origin or some old condition that was not noticed earlier and flared up suddenly.. such injuries can be dangerous if not dealt with promptly and in proper manner. you must immediately show it either to family physician and take opinions of specialist if advised so.. dont take it lightly. if you do not have any family physician please visit the casulty department of nearest hospital
Next Steps
in the mean while you can apply ice to the locally affected area..
Health Tips
do not self medicate..or take meds as suggested by pharmacist or friend or relative... seek proper medical advice