Although I generally wear large men's gloves, I think I have medium size hands, so the little J-frame generally isn't a problem when it comes to "fit".
I don't allow the gun to sit quite as "low" in my hand as some people I see, so the cylinder latch never gets near my thumb ... which is curled down at the last joint. While my index finger may have the ability to occasionally touch the tip of my thumb at the very end of my trigger stroke, by that time the internal hammer has already fallen, and the pressure experienced between index finger & thumb tip isn't enough to bother ME. Subjective issue, though ...
I don't use a "horizontal thumb" position, as I've seen some folks use with small revolvers ... and which I've also occasionally seen result in varying degrees of thumb "gouging" when the latch, or even the rear of the cylinder, gets shoved back into the thumb.
I think if you have large hands you may need to try some different grips. Just realize that using larger grips MAY compromise one of the favorite attributes of these small guns, which is streamlined pocket carry for lawful CCW/off duty use. Then again, some folks have large hands & large pockets, and they don't consider slightly larger grips to be a problem. It's all a matter of personal perspective and desires.
When it comes to small "pocket" guns, J-frame revolvers can generally offer many advantages because of their size and caliber ... but on the other hand, they also have some potential disadvantages, as well. Smaller grip frame (as you're discovering), shorter sight radius AND less easy-to-"see" sights, long DA (or DAO) trigger travel, increased perceived recoil (perhaps magnified by the smaller grip profile) ... and they only hold 5-rounds.
The trick is to balance the advantages against the disadvantages and then decide whether the compromise achieved is good for YOU ... and even if you decide it's advantageous for you, they still take a LOT of frequent & consistent practice in order to achieve and maintain reasonable proficiency.
Did you also try and rent one of the steel framed models, like a 649 or a 640? You might find the "balance & heft" different, and it might offset the smaller grip issues to some extent. You gain extra weight, true, but that might be something that offers you a "better" compromise.
I've used larger grips on different J-frames over the years, but they've always turned into "belt guns" when I did that ... for ME.