What Causes Painless Pink Blotch On Upper Shoulder Blade?

My daughter who is 3 almost 4 years old, has this mark on her left upper shoulder blade that appeared a week ago but hasn t changed much in that week. It looks almost like a pinkish/red blotchy, hickey or pinch mark that she says doesn t hurt to the touch and that she has no idea how she got it. I checked her car seat/clothes/etc. to see if they could have possibly caused it and I haven t found any possible sources yet. She is very active and does get hurt sometimes but I haven t come across a bruise like this before. Especially one that doesn t hurt if I slightly push on it or brush my finger across it and that hasn t really changed in 7 days. The fact that it hasn t changed in a week has made me slightly concerned and I m not sure if that s justified or just because she s my first and only daughter and I m a worry wart mother.