Hi, Welcome to health care magic, It might be due to balanitis or balanoposthitis due to trauma to the glans penis or shaft o penis. But it must be examined by naked eye of an expert for which you can consult general surgeon or dermatologist for proper diagnosis first. Treatment is mainly depend upon the underlying cause. You can go for symptomatic treatment like antiseptic cream or ointment topical application over glans to prevent super-infection with vitamin b complex and folic acid orally with pain killers available over the counter. Here,there are very less scope of blood or urine investigations,in spite of that clinical examination will be the confirmatory in making diagnosis clear. A dermatologist or general surgeon is preferred to consult.