What Causes Red Bumps On The Penis?

My bf just informed methat he has little red bumps on his penis. He doesn't feel any irritation but he does have abdominal pains and feel the uge to urinate. I have no symptoms and was tested a few wks ago since we did have unprotected sex. My results all came out negative. However since then, we have been intimate again. Should I be worried that this could be an std?