I am making a homebrew race and i'm trying to make a feature that is pretty much the Lizardfolk's Hungry Jaws feature and I can't figure out how to do it. Can somebody please help?

This is Hungry Jaws: As a bonus action, you can make a special attack with your bite (bite is unarmed 1d6+str piercing). If the attack hits, it deals its normal damage, and you gain temporary hit points (minimum of 1) equal to your Constitution modifier, and you can't use this trait again until you finish a short or long rest.

As off now you cannot add an automatic regaining on hit points equal to your con mod so make a dnd code on the snippet section called {{modifier:con}} so that you know the amount of temp hit points you regain. Then just adjust the automatically when you hit with that attack on the sheet, I've given you a huge reference already with my own creation using a home brew race.

When in doubt, use the thing you want to replicate as a template for a homebrew just so you can take it apart to see how it works. In your case, make a race using the Lizardfolk as a template to see how that trait was set up. You can always delete it when you’re done with it.