This is definitely an old penile fracture scarring issue that caused the indentation. Stick with mild bundling to build up tolerance first, allowing the tissues to slowly break down and allow new tissues to heal properly before going into advanced bundling methods. Those who have similar conditions as you tend to seek the quickest method possible, using low-intensity soundwave therapy (LiST), or similar devices using ultrasound technology. I was in the same shoes as you are now. When I was younger, my nympho of a gf (now wife for the past 30 years) went too hard and fractured my penis, not once, twice, but three times. Since then, slow and steady bundling method to break down tissues, stretch properly using incremental traction force, and keep the penis elongated in a straight or specific curvature of your choice during the healing process. Since then, PE has been and still is the only thing that keeps my penis strong and conditioned for crazy intimacy sessions. The longer and larger the penis, the stronger the supportive tissues and tunica structure must be.
So, when you do the bundling, make sure to twist until you can't twist any more. Test both directions. Whichever direction has the least amount of twisting/contorting degrees, stick with that lesser one. When pulling, pull only with enough force where you can actually feel the slight dull sensation, similar to pulling your fingers where your knuckles feel like they stretch just enough to pop and feel pressured enough to create a relaxation from being overworked. The tissues must reach that achy sensation under bundled stress load. Otherwise, the scarred tissues will not break down. Once you're done with the stretching, you must keep the penis elongated and under tension. It doesn't matter if it's 1.1kg or down to 500g. The penis must be kept straight, or with a slight curve, so you can get that sexual experience with a specific partner, while the tissues are healing. There is no compromise in that. An extender is great, but you can use anything with your wrap, such as a DIY PVC home splint, something rigid without biting into your skin with the wrap, or a stiff half or full tube of some kind.