Imperfect but forgiven
I was thinking you could try liquid bandaid. It's more flexible than a regular bandaid. The one called New Skin comes to mind, but there are other brands. You can get that at Walmart.
I tried the liquid bandaid first, for quite a while actually, but it didn't help. I thought it might too. There was one time since I first got this split that it had almost gone away and then I banged that thumb on something... I use that stuff when I get little cuts that sting a bit, usually on my hands.