Is the commandment to honour your mother and father what you are thinking of here?
This still holds as an adult, but for a sin to be mortal then there must be the intent to sin, the grave matter and the desire to seperate onself from God.
Were you dishonouring your parents? Only you know the content of the argument and what was going on between you all. To argue with someone doesn’t always mean you have committed a mortal sin.
The fact that you are quibbling whether a mortal sin has been committed suggests to me that it is not mortal, but for your peace of mind go to the confessional and speak to the Priest about it all. Please don’t post your very personl details here as no-one can give you intimate advice seeing as they don’t know you nor the deepness of your heart and conscience.
Remember it takes two to have an argument so I hope you and your parents make the peace and love and forgive each other.
Go to confession and receive the peace of mind from Jesus because when the Priest gives you his advice it is the advice of the Lord Himself.
DISCLAIMER: Catholic Answers has turned over the archive to Catholic-Questions.org and no longer owns, manages, or moderates the forums. For additional apologetics resources please visit www.catholic.com.