Thanks for your question and concern. There can be different reasons for the ulcer you have got on your penis and the first one coming to my mind is genital herpes. You need not worry about this by simply watching the advanced stages of the genital herpes pictures. The herpes lesions usually get build up on the red base of your penis in the beginning which is usually very painful. After they get ruptured, they can appear as small ulcers. Syphilis sores usually appear to be some ulcerated area having some irregular edges and not so painful. The genital warts form flat, soft and fleshy growths which are attached on a very huge base to the skin that underlies the penis. The skin tags which are very rare may get aroused from your penis’s foreskin. These skin tags are fleshy and elongated growth of the skin which gets attached to the narrower base of the skin that underlies the penis. There may appear some areas on the penis where you might feel irritation and this is due to the bad hygienic conditions that can be some reaction by soap or any other beauty product. You need to undergo a proper diagnosis of your condition which needs a proper physical examination that should be carried out by your physician. I would highly recommend you to set up a personal visit with your doctor and know the issues in detail. You can also ask your personal doctor to help you in understanding about the herpes explaining though the different genital herpes pictures so that everything becomes clear to you. Good luck.