With the exception of Peyronie’s disease (which is often painful and caused by the build-up of fibrous scar tissue in the penis)it is perfectly natural for a cock to have a bit of a curve. Here's why it happens:

Inside the penis, extending from the root to the base of the glans, are two cylindrical chambers called the corpora cavernosa. They are made up of spongy tissue and a network of bl00d vessels, and sit side by side in the penis. When the corpora cavernosa fill with bl00d, an erection occurs.

However, the human body is NOT symmetrical, so the corpora cavernosa in any given dick will not be of the exact same size, thickness or length. Nor will they always be of consistent size along their individual girths and lengths. So, when an erection happens, the penis will curve up or down, left or right, because of this lack of symmetry!

You're welcome. Will