You need to correct your masturbation method. You can send me pic of your penile part if you don't mind.
Next Steps
Do masturbation with hand while seating /lying down in whichever position you are comfortable. Before starting masturbation, retract penile skin as much as possible without pain, than apply moisturiser cream/ lotion /vaselline over whole circumference of penile skin. Do masturbation by retracting and forwarding penile skin.
Health Tips
In case of pain, urinary difficulties, you have to consult General surgeon and undergo local examination. Happy to help online. Take care!