I'm scared and worried

I'm totally freaking out My Boyfriends balls have been staying swelled up the past few days. well today I felt them and found a hard knot kind of like a small lump and he is embarrassed to see a doctor. I'm scared what if it's something serious he has been injured there before I can't deal with thinking it's cancer or something bad like that. I been crying and when he asked why I told him it was nothing I really want children with him. But what if he has to have one of his balls removed I'll still love him and he will still be a man to me I just want him to be ok. if we don't have kids I'm fine I got 3 kids from a previous relationship I'm just concerned for his well being. I can't take losing him so this is what I'm dealing with.