What Causes A Hard Lump In The Perineal Area?

I have a small lump in the perneal area a little smaller than a grape. Non tender, firm to touch and smooth borders/round. It's moveable with the skin and I feel a secondary long (hotdog style) lump to the left of the round lump. It is also non tender and firm to touch. I will get it checked but would like some suggestions of what it could be. I'm 21 years old healthy make. It is more prominent when I have erections.