I have hard raised bump on my chest and back a short while after I started Accutane

I started low dose 20mg accutane 7 months ago. My face and everything has completely cleared since then except a few months into the treatment I got these hard raised bumps (in total 4, one on the chest, 2 on the shoulders and 1 on the back) that were not painful to touch and were red. They've persisted throughout the therapy and won't go away. Any idea as to what they might be?