Awesome brother that it's working.
All this is a good thing. Feeling soreness in the inner penis is a good thing. I even feel this every time after a session even today.
If you stretch like this you will gain big time. You want to relax into the stretch fully (reverse Kegels), and also feel your inner penis stretch, simultaneously as you stretch your outer penis/shaft.
Soreness in this is good. The inner dick isn't pulled out, you stretch the tissue which promote cell growth/cell division (called: Mitosis Cell Division), and with time your penis will become longer, if you always let your penis heal in an elongated state.
When we are saying we are pulling out the inner penis, this is just a metafor and a mental hack to relax fully into the stretch. A mindset for stretching if you will. But a powerful one. You will gain big if you continue to stretch like this.