Dear George, A penile lesion is always the cause of concern and worry in any normal young man. There are a multitude of such lesions, and some are benign and others are malignant or pre-malignant. Of the benign variety some are simple infectious processes which in the long run could transform to malignancies if not properly evaluated and treated, yet others are generally unremarkable. The potentially malignant types, however, need aggressive treatment. From your general descriptions what you have is most likely a benign, non -infectious process.
Hemangioma is a good possibility.
The change in size during an erection is also a normal process since there is increased blood flow to the penis at the time of erection. It is possible to remove hemangiomas, but it may be unnecessary to do so, since these are generally benign and asymptomatic. However, a visit to the urologist is definitely a good idea. This information is provided for general medical educational purposes only. Please consult your physician for diagnostic and treatment options pertaining to your specific medical condition.