hi and what your mentioning is not any std symptom
Condom failures are unfortunate. You, however, got tested for the common STD's that you'd see from unprotected sex. I'd try to hold off from all the ruminating and examining of your penis. At some point, you yourself could be aggravating things. Sexually active adults should have an annual std/hiv screening. But the burning skin is likely unrelated to anything. Leave it alone and you may find you stop noticing this.