Hi and
I don't know anything about the lump but he really should go to a urologist and just have them take a look. It might be something really simple and that could be the reason you haven't conceived.
I have heard of home SA kits but I do not beleive they are reliable. However, my lab will let you do the sample at home as long as you get it to the lab within an hour.
So, I would say, send DH to the urologist! Something like that really can't be ignored, especially if it does cause some pain. It might be an infection of some sort and can easily be treated with meds.
Good luck!