Thank you for your question.
Unfortunately there are no medicines to increase penis size. The female vagina is most sensitive at the first 2 inches at the entrance so penile length is 2 inches or more in the erect state is sufficient to satisfy your partner. You can measure your penis in the erect state with a tape to reassure yourself
Regarding the pimple, it may subside on its own as more often than not it is an infection of a hair follicle. Keep the area clean and dry. If you notice it increasing in size or becoming painful consult a doctor specialising in skin and DVD
hope this helps