STDs is not your problem at all. Rather irrational paranoia.
The acronym STD stands for SEXUALLY transmitted disease. Which means you need to have sex in order to get them. The exceptions are HIV, hep B and C from which you can get from sharing a needle with an infected person. You don't get them by straching people and then putting your finger in your mouth.
This incident is not an STD exposure. You may get bacteria but not STD.