The speaker keeps brushing off signs that something is wrong. A frown, tears, dark circles, a yawn, a long silence: each gets a small, easy excuse. Too excited to sleep. Just tired. Nothing to ask about. But the excuses start to sound rehearsed, and the poem soon admits they are lies. The line about "the truth behind the lines" is where the mask slips.
By the end, the "scratch" blamed on playful dogs turns into "a few cuts" and then "scars," which suggests the speaker is hurting themselves and hiding it. The pain doesn't go away, so the marks stay "today and forever." The repeated phrase "It's no big deal" opens and closes the poem, and it changes meaning along the way. At first it sounds casual, but by the end it feels like a plea to be noticed, said by someone who is hurting and can't say so. The mood is quiet, guarded, and sad.