Blisters Below The Penis Head

Dear Doctor , I am 39 years old male. I m 165cm, 81 kg. I have unprotected sex with a girl whom i went out for few months. All the while is ok until recently, underneath of my penis head (right side) started to have blisters (yellow colour). It bleeds if I squeeze it. After a week it dissappear. A month later it came back but this time, after it recover soon I notice a bump of 0.5cm. I ignore it but a week later it started to grow like another skin . It is pink in colour and painless. Soon I notice a small spot on my outer layer skin just a dot. I decide to peel the small dot - it hurts a bit with one drop of blood . Doctor, can I know what medicine that can cotarize it so that the skin can fall off? I think I got it from the girl (she told me that long time she don t have sex) but I notice when I penetrate her (usually the first time) she feel uncomfortable - is it her cause me the problem? She is not a sex worker but just a normal girl.