Standard dynamite rules: taken from someone else's homebrew

The following are common, balanced rules for using a stick of dynamite, which can be easily incorporated into a campaign:

[Joy's addition] Cost: These are illegal to use and carry in many of the cities of Faerûn. They are made on site snd the constituants are purchased only with a permit.

[Joy's Addition] Potency: this will decrease over time, there is a risk that these sticks do something other than explode. They may just flare, they may have a decreased radius or damage, they may just smoke, or they may do nothing.

Action: As an action, a creature can light and throw the dynamite at a point up to 60 feet away.

Detonation: The dynamite explodes after a short time (typically at the end of the thrower's turn), or a longer fuse can be set to detonate up to 6 rounds later.

Damage: Creatures within a 5-foot radius sphere must make a DC 12 Dexterity saving throw.

Failed Save: Takes 3d6 bludgeoning damage.
Successful Save: Takes half as much damage.