Hard brown lump on shaft

I have this small brown/flesh colored lump on the shaft of my penis. It appeared 3-4 months ago and I thought it was am ingrown hair but it hasn't gone away. It hasn't gotten bigger but I think it's gotten harder?

I am sexually active but I have been with the same partner for over 2 years.

Any help is appreciated.

Here is a picture 

Maybe a wart?