You haven't told us the length of the barrel, the actual thickness of that front sight, or the caliber, or what you want to hunt with the gun, so its a bit of a mystery about what you want from us. However, assuming you have a rear, OPEN sight, and a post front sight, a wide front sight is only a problem for most shooters if the notch in the rear sight is too narrow.
If you are new to shooting an open sight, think of an open sight as the lower half of a peep sight, and look over it, and " through it" NOT at it. Focus on the front sight, always. Let your eye center the front sight in the rear sight. Stop trying to look at both the target and that front sight. Focus on the front sight only. The rear sight is located closer to your eye, and is there mostly to help you index the stock and front sight so that the barrel is aligned with the front sight and target. When you have shot round ball out of a shotgun or fowler, with NO rear sight, you will begin to appreciate the rear sight for what it is, but not get so excited that you spend your time looking at it, rather than the front sight.
How to Fix a narrow rear sight notch? Use a jeweler's file to open up the notch. I have found that widening the notch so that there is an equal amount of daylight on both sides of the front post, seen through the rear sight when holding the gun to your shoulder normally, so that the notch is equal to 3 times the width of the front sight in appearance in the rear sight notch.
A wide blade is no problem, if you use the 6 o'clock hold already mentioned. You can Imagine a thin line down the middle of that wider post, and hold the target centered on top of that thin line. That is how I learned to shoot pop cans at 100 yards using an open sighted revolver.
If you need it, you can scribe a line down the back of the rear sight notch to indicate the middle of the notch, or paint or draw a diamond to do the same. You can even scribe an actual line on the back of that front sight, if you must. I found that unnecessary, after shooting a lot of long range revolver at small targets. The lines became a distraction for close range shooting, although they didn't hurt accuracy at all.