1Repeat / unconditional / Always active
execute at @a[nbt={SelectedItem:{id:"minecraft:blaze_rod",Count:1b}}] run execute at @a[scores={playerHit=1..}] run execute at @e[nbt={HurtTime:10s}] run summon tnt
2 Chain / unconditional / Always active
/execute at @a[nbt={SelectedItem:{id:"minecraft:blaze_rod",Count:1b}}] run execute at @a[scores={playerHit=1..}] run execute at @e[nbt={HurtTime:10s}] run effect give @p minecraft:resistance 1 255
3 Chain/ unconditional / Always active
/scoreboard objectives add playerHit minecraft.custom:minecraft.damage_dealt
4 Chain/ unconditional / Always active
/scoreboard players reset @a[scores={playerHit=1..}] playerHit