The curtain hide the pain inside, the curtain hides what's deep within

^ should read "The curtain hides the pain inside," because you have hides in the second half of the line and without correct tense the flow feels choppy and this line lost some strength. however it is an interesting introduction and I like the way you jumped right into the piece.

The curtain covers the battle wounds, From a love gone wrong

^ from does not need to be capitalized here unless it is a word you are trying to emphasize or give an importance to, but even fully reading the piece it does not feel like you meant it that way. . .

The curtain hides who I am inside, in fear of judgement

^ I like the simplicity here. Nice job.

The curtain is my shield from pain, the only thing keeping me sane

^ this is interesting and it gives an very unique description. The imagery here felt odd at first but after rereading the piece I think I got it and it is definitely well written despite how odd it first appeared.

The curtain is my guide, to show me who will fight to know I am inside.
^ very strong conclusion. I like the growth of the story between the first line and now.

Interesting piece. Well written.