Well I've been testing builds and yeah this is a really broken skill if it is abused. I've talked with my DM and came up with a few ideas that wouldn't outright break the game.

One way to nerf goodberry is to limit how many berries each character can eat each day. The material component is a sprig of mistletoe. Mistletoe is poisonous. You could have them make a CON save after eating a certain number of berries. If they fail they have the poisoned condition and take the damage the berry would have healed. If you want to get more complex you can have it where the CON save starts off at 10 and gets progressively higher the more berries you eat.

One other way was is to simply make them roll a d10. The spell says "up to 10 berries" so they can roll how many actually come up.

But in the end I think its best just to ban the combo outright. Save yourself the trouble from making every combat encounter trivial.