“Do I have an STD?”

I am a 16 year old diabetic. I have a girlfriend and last Thursday I kissed her. This Monday I begin having this lesion in my gums. I never had sex, but my girlfriend claims the last time she was in a relationship was four months ago, she said she had oral sex but never other kinds of sex. She also was/is bisexual. Since I am a diabetic I prick my fingers all the time, I also touched her and got my fingers with her fluids. I washed my hands after. Could I get AIDS from that? I have dozens of pricks in my fingers and I test very often. I washed my hands after touching her. I am so worried, would you please help me. What do you think is that in my gums.