Is plastic surgery a social injustice from a Catholic perspective?
I am not sure if you can find anything in the sacred texts to speak out against plastic surgery. However, in an implied manner, if one considers the body to be a gift from the divine, then an argument could be made that one is unnecessarily tinkering with a gift that is not one's to alter. I think that individual perception and understanding will differentiate the answers to this question. Obviously, as previously suggested, counsel with a spiritual advisor would be good to receive further clarification. I would also suggest that there can be an addictive element to plastic surgery. Studies and analyses have shown that the more one engages in plastic surgery, the greater an addiction happens. If one accepts this, then I do believe that there are specific dictates about resisting temptation and fighting through an addiction.
I assume you mean a social injustice, as in, would it be considered sinful from the Catholic perspective, or the Biblical one, to undergo plastic surgery.
I have read the Bible several times in my life, and I cannot recall any reference to something that, in Biblical times, would be considered plastic surgery. I can see where a more conservative or strict interpretation of religious tradition could consider it mutilation (if it is elective plastic surgery, i.e. you don't need it to reconstruct tissue, but are looking to enhance appearance).
The Biblical references you are asking about would mostly deal with demonstrating pride before God.
And of course, if you are Catholic, and this concerns you because you are thinking about it as a personal choice, then by all means, consult with your Priest.