It could be a Urinary Tract Infection. If the doctor didn't prescribe the antibiotics to you, be sure to tell him/her that you took them, because with them in your system, it is very likely that a UTI or any other infection would be hidden. Don't panic, because most things like this are minor problems.
Hello,
Pain in the tip of the penis may be a symptom of sexually transmitted disease; this should be treated with the right antibiotics. This is better achieved by having gram stain of a penile discharge if there’s any and treatment should be directed to both you and your partner, to avoid re-infection. Of course there are also other reasons why you have this pain in your penis aside from having an infection like urethritis or prostatitis; hence, I advise you have yourself checked by a urologist and your partner by a gynecologist to really know what is going on so that proper medications be given to you.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.