My bf's penis is a little bit curved to the left but no pain during erection.?

Curve is normal: Most guys do not have a straight penis. They bend up, down and sideways. If you develop a new bend that seems to be getting worse over time, it may related to a condition known as peyronie's disease and treatment, though limited, is available. A urologist can induce an erection with medication, in the office to evaluate the bend to help determine if it's a problem.

If it works....: If you both enjoy it, and it works for the biologic function that is is suppose to be used for, then there is no problem.