Are you a brother who touched winkies with his sis, or 2 sisters, or what? Are you more than 2 years older than your sib?
You are freaking out for a. Touching winkies and b. Thinking there might be a physical consequence therefrom
stop teasing this person is young and needing some de-shamification
some minor sexual experimentation as long as it's not abusive or coercive or penetrative, just exploratory...This is normal to a small extent even amongst sibs, playfriends, before puberty even
you'll know if you did something you both did not agree to...
The chance of anything being exchanged is virtually nil, so stop worrying about a disease...
Just get straight with yourself over the winkie thing, was that in the wrong? If so, you need to go apologize and maybe you need help, or if it was innocent stupidity, just get a red face and know lots of people to stupid things and don't worry so much