I have been pondering it for years...
The Kingdom of Heaven is a physical kingdom where Jesus will sit on the throne of David in Jerusalem and will rule Israel as their Messiah, their King...
The kingdom 'within you' is the Kingdom of God which is the Holy Spirit in you...
Col 1:26 Even the mystery which hath been hid from ages and from generations, but now is made manifest to his saints:
Col 1:27 To whom God would make known what is the riches of the glory of this mystery among the Gentiles; which is Christ in you, the hope of glory:
Two Kingdoms; one physical, one Spiritual...Two promises...
The Scripture is clear regarding what we need to understand about the two Kingdoms. Here is a diagram of the differences.
A verbal description of this is found at Happy Heralds, Inc,:
"The Kingdom of Heaven and The Kingdom of God"
Have at it --