I had a pimple on my penis and i poped it but now it's just a big bump on my penis i only had sex with one girl and shes a virgin can i still have sex?

Yes but: I recommend you wait until the pimple has cleared completely and then remember to always use a condom. Do not forget to get your HPV vaccine series before you start having sex again and make sure your girlfriend gets the vaccine, too.

Sebaceous cyst: Likely diagnosis of your penile bump. Yes you can still have sex, however hope you will use protection. Might like to see a urologist if the bump persists & it bothers you.