Male cat - crusty nipple

I was playing with my 4-year-old male indoor cat yesterday and noticed something weird on one of his upper nipples. It was covered with a yellowy beige pointed crusty substance (about the size of a pencil eraser). It crumbled away fairly easily and revealed a slightly inflamed nipple that is a lot smaller than his other ones. The nipple beside this one had what looks like the beginnings of this same crusty substance.

Other than this, he seems to be his normal happy adventurous self.

Any ideas what this could be? Is it normal for a male cat to have nipple discharge of any kind?

[Savas]

It sounds like a small amount of infectious material leaking out. You should get kitty checked. It could be anything from a blocked "gland" that's infected to some sort of abnormal growth. (Cancerous or otherwise). It's more likely it's a simple form of feline  Eosinophilic skin Disease...but get it checked to be sure.