Could it be the raphe? The raphe is a ridge of tissue which extends from the anus, through the mid-line of the scrotum, then upwards through the underside of the penis. It can be quite noticeable in some men.

It is formed during fetal development when the scrotum and penis close in the middle and fuse shut.

Whatever it is, it does not sound like a reaction to Aldara. If you look at the package insert for Aldara, there are pictures of before, after, and "during treatment." A lot of redness, scaling, and itching can be normal when using it. If it is bothering you, call your doctor. He/she can give you some other treatment instead.

Good luck.