What To Do For The Pain Due To Pimple Under The Belly?

hi, i am 17 years of age and im a bit concered about something. you see i have what seems to be a pimple just under my belly it is causing me alot of pain. i cant sleep and it hurts me to walk! it had a black top on it like a black head so i picked off the head assuming just like a pimple it will pop but it hasnt. i have kept it clean by using antiseptic gel from the pharmacy. but its not working is there anything i can do to stop the pain?