Side effects to Oxycontin?

OK so I had surgery about a week ago and my doctor prescribed me Oxy. I'm 19 and I've never had surgery, nonetheless take a strong drug like this. It seems like when the oxy is wearing off, my nose begins to itch real badly for about 30 min to an hour. Is this some kind of allergic reaction or side effect I'm having to this and should I be concerned? Thak You all for your input!