And you are "welcum". Maybe someday you can find a man that likes this done to his nuts and you can help. I promise you will be so horny you will barely touch your clit for an amazing orgasm, or five.
No, does not hurt at all except penetrating the outer skin, and that is just a little. It doesn't even hurt to twirl the needle inside tearing up the tissue in there. The pain receptors are only to detect impact and pressure, not penetration from sharp objects. That is why you see so many of us stabbing and skewering, it actually feels good. As long as you don't do it in the wrong place. Yes, it will cause infertility after many years and twirling causes permanent atrophy. But, if one is through using them for impregnating a woman or doesn't intend to, we might as well have fun with them.
For me because I use something kind of dull compared to a hypodermic needle, it stings a bit just entering the skin. Then as it pushes it's way past the tough inner lining and muscle it feels like you are squeezing your nut a little and then, when it pops through there is no more discomfort at all. You can even move it around inside and it may even feel good, it does to me. If you push through the other side there is a slight stinging as it it exits, but that is all. last, virtually no discomfort at all as you pull it out, except a sense of loss maybe that it's over.