My Iguana has a blister looking thing on his nose?

Marley, my Iguana is about a year and a half old, in the last 2 weeks he has developed a blister looking thing on his nose,right at the tip, almost the size of a pencil eraser,I am not really sure if it hurts him or not,i can touch it and he jumps, but he could just be doing that, i don't know,so anyway, i hope someone out there can help me?