Baby boy grabbing penis/balls

Elizabeth

I have a 14 month old boy, for about 6ish or so months every time I take his diaper off he immediately goes down there with his hands. I know it's mostly normal, however, he grabs, pinches and pulls, HARD. I try to keep his nails short bc he will actually have claw marks and nail marks down there. He has a touch of eczema in his upper diaper area but I keep cream

On that. Help me! Why is he trying to rip his manhood off?!?