Wa alaykum salam
According to Ayatullah sistani if an unmarried woman wants to get married and she is not independent i.e she is dependant on others in making decisions and in other chores of her life,it is obligatory on her to seek the consent of her father or grandfather for this purpose.Rather,even if she is independent,she must seek their consent,as a matter of compulsary precaution unless if her father or granfather have given her the permission to get married to whoever she wants.
Therefore if either your father or grandfather are alive and if you are not independent(acc to islamic law) your nikah is batil unless your father or grandfather accept and agree to your nikah.
If they dont agree and as u said the boy doesnt have any major flaws you can acquire permission from the hakim shar'a(religous authority) Or your marja.
And if a womans father or grandfather is not alive,then the marrige is legal according to islam.An in this case,it is the duty of the woman to please and obey her husband .
But if it is done in such a way that the pleasure of the parents is also attained,this will be more liked by Allah swt.
Therefore,you should try your best to convince your parents by talking to them,or by asking someone else whom they trust,to speak to them.if they still dont agree,never lose hope,keep on trying even whilst staying with your husband .InshaAllah with the help of Allah you'll manage to acquire their pleasure.