Missing balls.
Were the needles made canon yet? I would say he probably fears his family or the entire Earth dying (in the anime he did have those dreams and he was worried about arriving in time to Earth and Namek and his reaction as a kid in the restaurant when he thought Krillin could be killed matches up with that) or at least being killed and maybe fears not getting any stronger, but it's hard to say since it's never come close to happening to him. And Chi Chi tbh, I doubt he wants to get a rollicking from her.