I feel a lump under the skin on my penis shaft at the base of glans. it feels like something hard under the skin. what could this be?

Probably not serious: Maybe sclerosing lymphangitis, which sometimes follows vigorous or repeated sexual activity. It's not serious and usually clears up on its own. Search online for more information; here's the Wikipedia article: http://en.wikipedia.org/wiki/Sclerosing_lymphangitis You can also find photos on line. Best to see a doctor to confirm; other conditions are possible.