Never having had a tank bulge (depressions yes, but no extrusions), I am afraid that I'm useless.
I suspect that depressions can be more useful in the long run than bulkes in gas tanks.
Buying another gas tank may be to expensive for my taste. I may fix the bulge by having a professional fix it, but suspect that I'll go for an even cheaper option.
That could be buying some tank cover, that would also hiode the bulge. One example is here: https://japan.webike.net/products/21226952.html .
I have seen others, made from plastic, in multiple colors. Unfortunately I haven't been able to dig up the webpage(s) later..
Have a nice day.