You do not need to fix this, it is perfectly normal. While an upward curve
is a bit more common, there are also many penises that curve
left, right, and have no curve at all. A downward-curving penis has unique advantages during sex that the other curves don't. Likewise, an upward-curving penis has advantages and disadvantages of its own in various sexual positions/acts. Please rejoice in your unique anatomy! Your partner will love it if you love it!