I stretched my cardigan?

Uhm, I bought this cardigan from Forever21 not too long ago and when I washed it, I put it up with a plastic white hanger, right? Well now, there's these bumps on the shoulder seams because the curve of the plastic hangers poked into those spots while it was drying. I really like this cardigan too, what can I do about it? Should I iron it or something? And I don't really want to buy a new one.