I have one testes in left side so unable to impregnate a woman ?

Depends: This is more of a statement than a question. It cannot be answered with the info provided. However, you should assume you are fertile until proven otherwise. It is important to know why you only have a solitary testis. If you have not had this addressed surgically, you need to see a urologist, soon!

See below: You can impregnate a woman with one testis. Therefore you should take precautions if you do not wish to cause a pregnancy. If the other testis was lost to trauma or cancer, chances are you will be able to impregnate a woman.