My fingernails are splitting; what should I apply?

Last time, when I peeled off my gel nails with my fingers, the tip of my thumb nail kept splitting apart.

I'm trying to grow it out while trimming it short, following your advice.

I subtly use my left thumb often, so whenever I use it with force

It turns white again and peeling occurs.

Should I apply gel nails only to my thumbs, let the tips grow out, and then cut them?

I'm wondering if I should apply a tonic or a nutrient supplement.

The left side is the spread side, and the right side is the original thumbnail shape.