Crusty sore on cat's nose

I was hoping someone here might have some ideas for me.  One of my cats has recently developed a weird crusty sore on the side of his nose kind of by the end of his eye.  He is less than a year old and had been at the pound for several months.  He has not been outside since I got him but he and the other cats play and can get kind of rough.  I noticed the spot about two weeks ago when it was more of a bump and it has since gotten kind of a crust coating on it and is less of a bump.  It hasn't gotten any bigger and doesn't seem to bug him.  His eating and energy level are fine.  He doesn't like me touching it but he doesn't really like me messing with his eye area in general.  He has had his shots but I think he got a bit of an upper respiratory issue when I first got him at the end of May.  Any ideas would be appreciated.  Thank you. 

Is the eye itself watery, squinting, or draining anything? If so, then your kitty may need to see the vet for antibiotics for infection. If not, and you did say it was a bump first, then it could be a number of things. Possibly a bug bite? It may be a good idea to call the vet and see if they want to see him. If you think he may have an URI, then he most likely does. Best to get him checked out. Keep us posted.

His eye seems to be fine without any other discharge.  I wonder if it could be a spider bite like you suggested?  It has been there since around the 4th but I guess I have had bites that have taken several weeks to go away and have gotten kind of a crusty coating on them.