Song lyrics are often difficult to understand — even for native speakers. The meaning is often not literal, but rather figurative and/or full of double meaning.
Here is what I understand:
stitches: when you have a bad cut and a doctor has to sew it shut, he stitches it. You have stitches. Of course, clothing also has “stitches”.
dress me up: There is a play on words here:
“dress (a wound)” and “dress up (in fancy clothes)”
black and blue: this is how bruises are described
The literal meaning of the song is extremely violent and/or masochistic. It seems to mean that the singer wants to be badly injured (beaten and cut) by someone. :shock:
Figuratively, it might mean that the singer wants someone to love them, no matter how much it might hurt.
I must admit, lyrics like these are not exactly my cup of tea. :?