Issue with stretching, help

OK so I’ve noticed this for a while, but really noticed it when I decided to stretch for longer amounts of time. As I stretch I notice that the head of my penis gets very uncomfortable, and when I remove the stretch it becomes a more pink color that normal and puffs up just a bit. It really became a concern when a small lump appeared near the circumcision scar. I’m sure like always these lumps will go away but I don’t want to be damaging my penis, any suggestions for better stretch methods?