I Had Plaster of Paris Set on my Face Now I Have a Burn How Do I Treat This? (photo)

my friend made a mould of my face using plaster of paris, i didnt know what it was so i went ahead with it. while it was hardening it burned a little and my eyes where bloodshot when it came off. i did reasearch and found out its not supposed to get on your skin or eyes b/c it causes chemical burns now i have a burn on my nose and i want to know if its serouse? how to treat it? and how to make it not scar? can anyone help out please :/