Instead of using a weapon to make a melee attack, you can use a punch, kick, headbutt, or similar forceful blow. In game terms, this is an Unarmed Strike: a melee attack that involves you using your body to damage, grapple, or shove a target within 5 feet of you.
Whenever you use your Unarmed Strike, choose one of the following options for its effect.
Damage. You make an attack roll against the target. Your bonus to the roll equals your Strength modifier plus your Proficiency Bonus. On a hit, the target takes Bludgeoning damage equal to 1 plus your Strength modifier.
Grapple. The target must succeed on a Strength or Dexterity saving throw (it chooses which), or it has the Grappled condition. The DC for the saving throw and any escape attempts equals 8 plus your Strength modifier and Proficiency Bonus. This grapple is possible only if the target is no more than one size larger than you and if you have a hand free to grab it.
Shove. The target must succeed on a Strength or Dexterity saving throw (it chooses which), or you either push it 5 feet away or cause it to have the Prone condition. The DC for the saving throw equals 8 plus your Strength modifier and Proficiency Bonus. This shove is possible only if the target is no more than one size larger than you.
SRD 5.2.1, p.190 · CC BY 4.0