That gap seems to vary with each penis, and one I'm familiar with because I too have it. Our approach was to taper the shaft as best as possible to mitigate the appearance of the gap, which has helped.
I'd say trying to fill in the area can be stubborn --> nodules are more common, and more effective options for that area like Silikon1000 micro-droplets are seemingly off the table.
I still have some gap and I suspect the nature of my circumcision played a role. Too bad I can't rewind time to slap my doctor as a baby
That said, fortunately it seems to be only something I have noticed; I've had partners in the double digits and no comment was made, and I suppose if ever one to be made, I'd simply tell them I had a botched circumcision as a baby.
Note* I'm not saying try not to get your situation improved, just saying it isn't nearly as bad as you think (coming from someone that started with a gap more noticeable than yours). Like I always say, we're our own harshest critics. Good luck either way and I'm glad Dr. C chimed in