Hi,Welcome to Health care magic forum.
                 It appears to be a boil, as it is desturbed, it is infected from the out side bacteria, and became septic. If it is left like that it may swell, still more. 
                 So i advise you to consult a surgeon for diagnosis and treatment.If there is much pus inside, he will incise and drain to remove the pus, then put a plug in the cavity, and do dressing periodically. 
                 If the swelling is minimal, the conservative treatment will be sufficient. 
                 I usually prescribe to my patient with such symptoms 
ofloxacin, 
ornidazole, serratia peptidase, and diclophenac sodium. 
                  Wishing for a quick and complete recovery.